Crummy Gas Mileage
#61
12-29-2010, 10:27 AM
Veteran Member
I suppose I read posts like this and have to scratch my head a little. Why does everyone say the onboard readings are fantasy (I'm talking about average MPG here, not range - which is much harder to calculate)? 20.07 real world MPG and the computer reads 21.6-22, that's only 8-10% off! It's a little optimistic, but that's in line with what I'm seeing when comparing onboard to real-world, and I think it's a pretty good indicator.
George
#62
12-29-2010, 10:27 AM
My issue isn't so much indicated MPG, but the fact that the dashboard seems to hide 4-5 gallons of fuel, both in range, AND in indicated fuel on board. - Low fuel warnings are triggered etc ... if one were to believe that the 18.6 gallon capacity, then go fill up with 12.8 gallons, you realize you have almost 6 gallons left or 1/3 of a tank, and wonder what all the fuss was about...
George
George
#63
12-29-2010, 10:41 AM
Veteran Member
True, you have a point about the fuel level / range for sure. Perhaps Jaguar engineered it conservatively to keep people from running out of gas, which is bad in its own right, but I believe the fuel pumps are also cooled by fuel and can burn out if run dry (at least on the STR).
My 500sl which gets slightly worse mileage, carries almost 25 gallons of fuel aboard and has a longer range. I just wish I could get through a work week without having to stop for gas. Oh well.. Rant over..
George
#64
12-29-2010, 05:02 PM
Veteran Member
George, I hear ya' bro. I guess I did inadequate research and thought I was getting a 25 gal tank on my '95 XJ6....but no...guess that was a '96 or '97 mod and mine holds barely over 21. 100 mi/day so pretty much what you are seeing with your S-type, 3.5 days of commuting and it's time for a fill. You could always pick up a diesel Excursion, 44 gal capacity....but then you'd be like me watching Clarkson and company sweating the load on a drive from wherever to Blackpool of 800 mi on one tank and scratching your head (if not lower) and wondering, "what's the big deal?"
#65
12-29-2010, 05:19 PM
Senior Member
My issue isn't so much indicated MPG, but the fact that the dashboard seems to hide 4-5 gallons of fuel, both in range, AND in indicated fuel on board. - Low fuel warnings are triggered etc ... if one were to believe that the 18.6 gallon capacity, then go fill up with 12.8 gallons, you realize you have almost 6 gallons left or 1/3 of a tank, and wonder what all the fuss was about...
George
George
George
i agree with you... we all know the tanks hold 18.6 gallons... just like my STR the gas tank warning light up around 12 gallons.
it seems the tank is hiding the rest of the fuel some where.
Anyone has any idea what going on with this.. maybe the fuel pump...
thanks
#66
12-29-2010, 08:49 PM
Veteran Member
#67
12-30-2010, 02:58 AM
Veteran Member
#68
12-30-2010, 05:21 AM
Veteran Member
Here's what I've done thus far.
1. When almost exactly on E it takes approx. 14.5 gallons to get it to F. A lot of guys report this result. I think it's a system characteristic. At least that's what we used to call such things in the software industry when it wasn't quite right but it wasn't something we could fix because it was too big a flaw in the design.
2. George has advised me that when in "engineering mode" you can get digital readings from each of the sensors (one in each tank?). In the spring I may go through this exercise before my warranty runs out. At the moment I'm a bit more focused on digging out of 24-30" of snow.
3. When it drops precipitously from F to 3/4 I really need to take a look at those readings and then fill the tank up again to see how much fuel it thinks 1/4 of tank is at that point. I already know it's not representative of even 1/4 of the 14.5 gallons.
So we can do this and then see if a number of us have the same results or a handful of us have faulty systems.
Anything I missed?
Bob S.
1. When almost exactly on E it takes approx. 14.5 gallons to get it to F. A lot of guys report this result. I think it's a system characteristic. At least that's what we used to call such things in the software industry when it wasn't quite right but it wasn't something we could fix because it was too big a flaw in the design.
2. George has advised me that when in "engineering mode" you can get digital readings from each of the sensors (one in each tank?). In the spring I may go through this exercise before my warranty runs out. At the moment I'm a bit more focused on digging out of 24-30" of snow.
3. When it drops precipitously from F to 3/4 I really need to take a look at those readings and then fill the tank up again to see how much fuel it thinks 1/4 of tank is at that point. I already know it's not representative of even 1/4 of the 14.5 gallons.
So we can do this and then see if a number of us have the same results or a handful of us have faulty systems.
Anything I missed?
Bob S.
#69
12-30-2010, 06:05 AM
Further information supporting many contributor's opinions:--
Only this very morning my computer derived mpgUK figure was 25.5mpgUK.
The brim-brim figure was 21.4mpgUK.
Not only is my computerized figure wildly inaccuarate, but the inaccuracy is also inconsistent, if always too generous.
Also highligted was the effect very cold weather/cold running has the mpg figure. My journeys are always shortish with engine UNDER temperature most of the time. I feel that the best results are not obtained until the engine has reached around 85% of its operating temperature.
Consequently, I'm looking into cost-effective ways of pre-warming the engine before even switching it on. As a rough guess, only one kilowatt-hour of pre-warming should make a substantial difference, as that cost for me would be 11.5pence. If you're interested, keep reading these postings -- I shall report. Car is S-type 2.7D.
Leedsman.
Only this very morning my computer derived mpgUK figure was 25.5mpgUK.
The brim-brim figure was 21.4mpgUK.
Not only is my computerized figure wildly inaccuarate, but the inaccuracy is also inconsistent, if always too generous.
Also highligted was the effect very cold weather/cold running has the mpg figure. My journeys are always shortish with engine UNDER temperature most of the time. I feel that the best results are not obtained until the engine has reached around 85% of its operating temperature.
Consequently, I'm looking into cost-effective ways of pre-warming the engine before even switching it on. As a rough guess, only one kilowatt-hour of pre-warming should make a substantial difference, as that cost for me would be 11.5pence. If you're interested, keep reading these postings -- I shall report. Car is S-type 2.7D.
Leedsman.
#70
12-30-2010, 06:17 AM
Veteran Member
Bob, your 14.5 US gallons (in the situation described) does not match my experience, so my car is apparently in a different category.
I got in 58 litres (15.3 US gallons) without drama and was not on Range zero.
Whether mine was actually full or whether yours is would be guesswork, but clearly it matters knowing whether the tank is full when the gas pump cuts out if one is debating the capacity and readings based on it.
BTW, I'm used to analogue dials being inaccurate on every vehicle I've owned, so I rarely glance at the fuel gauge since there's the Range etc digital readout. I'd maybe glance at the gauge to get an "empty, panic" or the like quick view.
Some people have previously posted STR values when in ETM, due to a member having a clearly faulty system (then fixed under warranty as I recall).
I got in 58 litres (15.3 US gallons) without drama and was not on Range zero.
Whether mine was actually full or whether yours is would be guesswork, but clearly it matters knowing whether the tank is full when the gas pump cuts out if one is debating the capacity and readings based on it.
BTW, I'm used to analogue dials being inaccurate on every vehicle I've owned, so I rarely glance at the fuel gauge since there's the Range etc digital readout. I'd maybe glance at the gauge to get an "empty, panic" or the like quick view.
Some people have previously posted STR values when in ETM, due to a member having a clearly faulty system (then fixed under warranty as I recall).
#71
12-30-2010, 07:05 AM
Veteran Member
#72
12-30-2010, 07:53 AM
Veteran Member
The analogue gauges (in common with others in cars) don't even read the values they are told to read, judging by the various values from ETM, my OBD tools and looking at the gauges.
The digital display (LCD) at least tells you a value that appears to be more accurate than the dials.
I haven't taken a sensor out of the tank but I expect they're the typical float type.
The digital display (LCD) at least tells you a value that appears to be more accurate than the dials.
I haven't taken a sensor out of the tank but I expect they're the typical float type.
#73
12-30-2010, 07:58 AM
I get like 280 miles out of a tank... It is what it is really. These claims of 30+ mpg have me amazed. These guys driving 45 degrees downhill both ways or something? Do they get the car to 70 never exceeding 2000 rpm, set the cruise and putt along in the right lane and don't ever touch the brakes till they get where they are going?
I agree the whole ethanol / E85 programs are vast wastes of resources, but the government is so behind... Billions in farm subsidies have been given to basically cut gas with grain alcohol and reduce it's energy content, while people are allowed to starve and the price of food has doubled.
I also don't agree that at least in Jersey, with our 15% "MTBE" winter blend, that we really do anything to help the environment. E85 (85% ethanol, 15% gas) has an octane rating of about 105. It burns a lot quicker / hotter than gasoline. BUT it has a lot less stored energy - roughly 75% of the BTU value, so it requires a 30-40% greater volume of fuel to make the same power. The only thing it really does is help the engine get to operating temp quicker, theoretically getting out of closed loop faster and speeding up operation of the cats... It's one thing to have these new "flex fuel" cars that are designed to run on E85, which I have only seen at a couple pumps in Jersey, and another thing to cut gas with alcohol.
I know a lot of the race guys make "race fuel" by mixing E85 and regular 87 octane gas. In equal parts it gives you about a 100 octane mixture, which is great for preventing detonation (and lean conditions), and only about 15% lower energy storage (which can be compensated for in tuning). Once again, this is an arena for high compression, or forced induction engines that do not run well on 93 octane premium (or you have to take timing out of to avoid pinging). I haven't tried this on my drag car, (which is at 14:1 and struggles to start, and idle) but I was thinking about it next season. Usually spraying brake cleaner into the carb will get it to fire, and you have to dual pedal it on the street to keep it idling. I'd have to bump the carb's jets up a couple sizes. But no big deal there.
The biggest problem with Ethanol in fuels, especially primarly ethanol based fuels is their tendency to attack steel and especially rubber fuel lines. Basically the entire fuel system has to be stainless steel to avoid problems in the long run.
George
I agree the whole ethanol / E85 programs are vast wastes of resources, but the government is so behind... Billions in farm subsidies have been given to basically cut gas with grain alcohol and reduce it's energy content, while people are allowed to starve and the price of food has doubled.
I also don't agree that at least in Jersey, with our 15% "MTBE" winter blend, that we really do anything to help the environment. E85 (85% ethanol, 15% gas) has an octane rating of about 105. It burns a lot quicker / hotter than gasoline. BUT it has a lot less stored energy - roughly 75% of the BTU value, so it requires a 30-40% greater volume of fuel to make the same power. The only thing it really does is help the engine get to operating temp quicker, theoretically getting out of closed loop faster and speeding up operation of the cats... It's one thing to have these new "flex fuel" cars that are designed to run on E85, which I have only seen at a couple pumps in Jersey, and another thing to cut gas with alcohol.
I know a lot of the race guys make "race fuel" by mixing E85 and regular 87 octane gas. In equal parts it gives you about a 100 octane mixture, which is great for preventing detonation (and lean conditions), and only about 15% lower energy storage (which can be compensated for in tuning). Once again, this is an arena for high compression, or forced induction engines that do not run well on 93 octane premium (or you have to take timing out of to avoid pinging). I haven't tried this on my drag car, (which is at 14:1 and struggles to start, and idle) but I was thinking about it next season. Usually spraying brake cleaner into the carb will get it to fire, and you have to dual pedal it on the street to keep it idling. I'd have to bump the carb's jets up a couple sizes. But no big deal there.
The biggest problem with Ethanol in fuels, especially primarly ethanol based fuels is their tendency to attack steel and especially rubber fuel lines. Basically the entire fuel system has to be stainless steel to avoid problems in the long run.
George
I got about 32 mpg last year in the dead of winter on a run up to NYC from DC. I set the cruise for about 72 mph and stayed in my lane. Not even the NJ state troopers bothered me. When I filled up the tank, the computed range was then 450 miles. What killed me were all the friggin' tolls. It was like $30 each way.
#75
12-30-2010, 08:14 AM
#76
12-30-2010, 08:18 AM
Veteran Member
George,
I got about 32 mpg last year in the dead of winter on a run up to NYC from DC. I set the cruise for about 72 mph and stayed in my lane. Not even the NJ state troopers bothered me. When I filled up the tank, the computed range was then 450 miles. What killed me were all the friggin' tolls. It was like $30 each way.
I got about 32 mpg last year in the dead of winter on a run up to NYC from DC. I set the cruise for about 72 mph and stayed in my lane. Not even the NJ state troopers bothered me. When I filled up the tank, the computed range was then 450 miles. What killed me were all the friggin' tolls. It was like $30 each way.
You need to get EZ Pass if you're going to spend any amount of time here. Tolls will just kill you speed wise otherwise.
George
#77
12-30-2010, 10:42 AM
Veteran Member
Several factors. First, ethanol content of the gas - a lot of the "winterized" blends contain up to 15% alcohols.
Second, the tires can play a role. Pressure, and actually rolling diameter and unsprung weight.
Lastly, Ambient Temperature. - The cold air rushing through the motor makes good power compared to less dense air but with a corresponding increase in fuel consumption. Also the colder ambient air actually pulls more energy away from the motor as far as taking heat away from the motor.
George
Second, the tires can play a role. Pressure, and actually rolling diameter and unsprung weight.
Lastly, Ambient Temperature. - The cold air rushing through the motor makes good power compared to less dense air but with a corresponding increase in fuel consumption. Also the colder ambient air actually pulls more energy away from the motor as far as taking heat away from the motor.
George
#78
12-30-2010, 11:21 AM
LOL... Welcome to Jersey. And you could go 78 safely without the troopers raising an eyebrow here. This isn't VA LOL. During a typical workday there's too many people going 90+ and swerving lanes for them to worry about anything less.
You need to get EZ Pass if you're going to spend any amount of time here. Tolls will just kill you speed wise otherwise.
George
You need to get EZ Pass if you're going to spend any amount of time here. Tolls will just kill you speed wise otherwise.
George
I also ran afoul of NJ's quaint custom of requiring gas station attendants filling up the gas tank. When I proceeded to fill my tank up one said "you're not from around here, are you?" I thought the VA license plate would have been a clue.
VA has a 10% ethanol blend in all their stations so you may see perhaps up to a 4 mpg improvement using a pure gas during the summer months. One amusing thing I saw was an article about the 10 or so best economy vehicles and the 3.0 S-Types measured up fairly well, at least for highway mileage.
Mike
#79
12-30-2010, 11:49 AM
Veteran Member
George,
I also ran afoul of NJ's quaint custom of requiring gas station attendants filling up the gas tank. When I proceeded to fill my tank up one said "you're not from around here, are you?" I thought the VA license plate would have been a clue.
VA has a 10% ethanol blend in all their stations so you may see perhaps up to a 4 mpg improvement using a pure gas during the summer months. One amusing thing I saw was an article about the 10 or so best economy vehicles and the 3.0 S-Types measured up fairly well, at least for highway mileage.
Mike
I also ran afoul of NJ's quaint custom of requiring gas station attendants filling up the gas tank. When I proceeded to fill my tank up one said "you're not from around here, are you?" I thought the VA license plate would have been a clue.
VA has a 10% ethanol blend in all their stations so you may see perhaps up to a 4 mpg improvement using a pure gas during the summer months. One amusing thing I saw was an article about the 10 or so best economy vehicles and the 3.0 S-Types measured up fairly well, at least for highway mileage.
Mike
What's funny is that you jump out ready to fill, we are so ingrained that when we pull up to a gas pump in your state (I have family in Loudon County - Potomac falls, and in Alexandria), it takes a moment of thought to realize that we have to get out and pump it ourselves...
My brother owns an independent shop, and has gas pumps out front. I 95% of the time fill up there and do pump it myself, but they all know me, so no harm no foul.
I think we do 15% ethanol in our winter blend. At least we used to.
George
#80
12-30-2010, 08:17 PM
Here, in Missouri, Premium fuel (91 octane or higher) isn't required to contain any ethanol. I'm very picky about where I get my fuel, and if I see that sticker, I move on down the road. I avoid it like the plague since it sells for the same price while lowering performance.
On another note, with fuel prices as they are, I over-inflate my tires and get a better ride while saving money (and the planet - gag!). I ran the math using my van, and by running my tires 5lbs over, I still save nearly $1000 throughout the life of the tires, even though that life is shortened.
On another note, with fuel prices as they are, I over-inflate my tires and get a better ride while saving money (and the planet - gag!). I ran the math using my van, and by running my tires 5lbs over, I still save nearly $1000 throughout the life of the tires, even though that life is shortened.
If your tires last 45,000 miles inflated at 30 psi and only 30,000 miles inflated at 35 psi, it costs $200 versus $300 per year to operate the tires assuming you travel 15,000 miles per year. The annual difference is $100.00, which is roughly equivalent to the fuel savings achieved by inflating the tires to 35 psi assuming gas is $3 per gallon.
That said, gas is going beyond that, so inflating the tires that extra 5 psi is a smart thing to do given today's fuel prices.