I have believed that all gas is pretty much the same and the advertising about better fuel detergents was just hype to justify slightly higher prices. Now I have seen two articles on a AAA study that showed significant difference in carbon deposits by using top tier gas. (BP, Chevron, Shell, etc) I usually buy gas at Costco because it is the best price around but a few months back I filled up with Shell Premium and noticed an increase in gas mileage form around 24.5 to 27 mpg. highway driving.
Any similar experience with MPG or knowledge of less carbon build up from top tier gas?

 

Costco is a fully certified Top Tier seller, so I have no idea why you're seeing any difference when using Shell. It sure isn't the additives.

Most if not all brand name fuels have the same volume and type of detergents as Top Tier but have just not bothered as yet with buying the right to advertise being Top Tier. The certification is not free.

On the subject of additives, the US truth in advertising laws forces BP to put the following disclaimer regarding their latest high end product 'BP with invigorate':

"Compared to minimum detergent gasoline. Requires continuous use over 5000 miles. Based on fleet testing representative of the U.S. car population. Benefits may be more significant in older model vehicles. Restores an average of 3 - 5 miles per tank that had been lost due to deposits. Fuel economy can be affected by many factors"

You've probably seen the ad with a car dragging the anchor around on the back. The above disclaimer flashes by on the screen, but too fast to read.

And yet people get sucked in.

FWIW, I see mileage fluctuations similar to yours but without my making any change in fuel, oil, driving style etc. etc.

 

I've found my gas consumption has improved since having the car.
Its a 2.5 V6 petrol 5 speed auto.
When I first bought it the average was 27.9 and now its 28.4 which I think is very good. I tend to cruise and only occassionally boot it. This car makes me want to drive in a more gentle manner, I don't feel the need to compete.
My 2 litre 16V zetec engined Ford with 4 speed auto did 23.4 mpg average. So a 5 mpg improvement is significant.
I use cheap fuel 90% of the time and premium 10%.

However the biggest improvement I've found over the years is by regulalry using fuel addatives to clean the fuel system. The brands I use are Wynns, STP and Redex. So about once a month I put a bottle of fuel system cleaner in the tank and that does help the car run smoother and more efficiently.

 

Just curious about your definition of premium. Do you mean brand name or are you referring to octane ratings?

Sorry to ask, but the two meanings are sometimes used interchangeably here.

 

Cheap fuel to me is low octane (95 ron) purchased from a supermarket petrol station ie Tesco, ASDA, Sainsbury etc
Premium fuel to me is high octane (98+ ron) purchased from a franchised branded independent petrol station ie: Shell, BP etc
Although you can purchase the higher octane petrol from supermarket petrol stations, its still supermarket petrol.

 

The words "Top Tier" refer only to additive content. You didn't mention which grade of gasoline you purchased from Costco.

If you bought Costco Premium, the gas mileage will be similar to Shell Premium.
If you bought Costco Regular, the mileage increase with Shell Premium is not at all surprising.

Costco is up-front about gasoline quality. One of their comments:

"Costco advises that you use the octane rating specified in your owner's manual. In fact, using regular unleaded gasoline in a car that specifies premium unleaded could void your vehicle warranty".

Yes, I know your warranty has long since expired...

 

And again the word 'quality' is used with respect to octane rating, as opposed to quantity or type of additives.

No wonder people get confused.

 

But it's all the same fuel from the same refinery as the name brands, the only potential difference being the additive package specified by the end retailer.

If we are to take BP's disclaimer above as being the result of credible laboratory and real world testing, the best fuel only returns a miserable 3-5 miles per tank more than minimum spec fuel.

Sort of blows the old myths out of the water.

 

Here's the full AAA report on Top Tier fuels. It makes a pretty compelling case for using Top Tier only which I'll now be doing. BTW - the Gas Buddy app shows which stations are Top Tier.

 

Wow, that's an interesting report. I've always been a stickler to stay with one brand, too, Chevron in my case. Because different retailers have different additive packages, I figured switching around isn't a good practice. I've been very pleased running Chevron almost exclusively. In the 8 years I've owned my S-type (and 5 years with a Lincoln before that), I've had a grand total of zero fuel issues in all that time with those vehicles.

I think you will find practically any modern fuel-injected vehicle is very tolerant with the fuel available today. Not so with older, carbureted vehicles. Older engines are very finicky about modern fuels, especially when dealing with underhood heat. My hunch is because so few carbureted vehicles are still on the road, retailers don't worry too much about making fuel heat-resistant these days. I've got four carbureted vehicles in my stable and have had to make some engine mods to help keep fuel-related heat issues at bay.

So while this aspect may be outside the intended scope of your query, from personal experience I can state the brand makes a HUGE difference with a carb. I've found Chevron and Shell hold up the best. 76 and Conoco meant a long cool-down by the side of the road. Curiously, they are all Top Tier but I guess that standard doesn't mean much with a carb. I've had three instances on long trips where all was groovy with Chevron, but when I had to fill up with 76 or Conoco, the engine sputtered and died within minutes. It was too soon after a fillup to be a coincidence. All was fine again for a while after cooling down for an hour or so. This happened with more than one vehicle, too.

Back to fuel-injection, a coworker (with a long commute) ran some very detailed fuel consumption tests with different brands. He used the cruise control as much as possible for consistency. He was considering switching to ARCO because it retails for about 20 cents cheaper per gallon in my neck of the woods. I've always figured there's a good reason why it's cheaper so never touch the stuff. He found his overall fuel expense was about the same, whether cheap ARCO or more expensive Chevron or Shell. While ARCO was cheaper per gallon, consumption increased. Meanwhile, he used less of the more expensive stuff. I think he determined a slight distance per dollar advantage with the spendy stuff, but not by much. He still runs the good stuff, though, due to reports of less carbon buildup, etc. So do consider your distance per dollar if you decide to run the cheap stuff. Don't make your decision solely on the price per gallon.

Another thing to consider is boutique fuels, especially seasonal blends. If you're in an area requiring specialty fuel, you should be okay. Outside the area can be a different story. In summer, a distributor might be stuck with leftover specialty winter fuel. It can't be sold in the specialty area, but it can be unloaded elsewhere. Same in the winter, as you might get leftover summer blend. So if you live in the country and think special area fuel requirements won't affect you, think again. People in the city are getting the proper seasonal blend, but you might be getting the leftover stuff from the wrong season. This may not be a factor with fuel-injection, but it can wreak havoc with a carbed vehicle.

 

Wow that's RARE. I understood the only auto on the 2.5 to be the 6-speed ZF.

 

For sure in the past (I had a relative who was in charge) the supermarkets just buy the cheapest from the named brands. So one week you get Shell, another BP, Texaco, whatever.

They didn't change it at all apart from not revealing the brand each time it changed.

You could even see the tanker with Shell or whatever on its side doing the delivery.

It was and I expect still is a MYTH that supermarket fuel is different or poorer quality (and of course it MUST and WILL meet the laws about it).

However, rather like butt dynos, people with no actual knowledge swear blind the above is untrue. Yeah, whatever.

Oh and at least one utterly unscientific useless "car" TV programme has done "testing". Emphasis on unscientific and useless.

Overall, do as you would with engine oil: buy what you like. But please don't make claims that are based on your "experience" so it must be true because that is just asking for grief.

 

But what about ethanol and oxygenated fuels? Do they vary from brand to brand or region to region. I know that the more ethanol in the fuel the lower the mileage (and consequently the higher the operating costs).

And trust me, you don't want to store a carbureted vehicle for long with tank of ethanol fuel.
==================================================
Jaguar: Grace, Pace, and Space - Sir William Lyons
2015 JCNA National Slalom Champion Class M
Current: '08 Jaguar S-Type 4.2 "Satin Edition" (250.06 whp / 259.67 torque)
Past: '05 X-Type 3.0/auto Jaguar Racing Green

 

I think any carburettor issues should be in a separate thread or - better - another forum, as S-Types do not have such.

 

That's an interesting study, thanks for posting it. I hope everyone takes the time to read it in full and then re-reads it to ensure that the essential findings are understood.

If not, here's the key points:

Long term usage of non Top Tier gas containing only the minimum amount of additives, might, in some cars, reduce mileage and power by 2-4%.

Switching to Top Tier gas might help recover some of the lost power and mileage but it will take 5000 mile of continuous use to do so, and drivers should expect only 50-75% recovery.

What this means:

Anybody who claims to note instant changes when switching to a top tier fuel has got a very active imagination.

Even long term, if we are to take the study's result as absolute proof, a typical S-type that sees nothing but top tier fuel from day 1 and averages 20 mpg would still get around 19.4 mpg if it had been fed so-called garbage fuel since day 1.

If a car was to switch from long term use of garbage fuel to long term use of top tier, the eventual difference in mpg pre/post would narrow to only .3 mpg.

Such minor changes would be virtually impossible for the average motorist to notice as typical variations from one tank to another without the owner making any changes can be as much a 2-3 mpg.

All of the above pre-supposes that there actually is garbage fuel readily available. Here in Canada, only a few retailers are Top Tier, none of which are handy to me. Am I to assume that all/some of the other brands are selling garbage? Or do they see through all the fuss and expense of the top tier scheme and just sell gas with enough additives for today's cars?

I find it interesting that Jaguar/Ford back in the day or JLR today does NOT require top tier fuels, unlike some of it's rivals. Guess they must have hired design engineers that knew what they were doing. Top tier engineers?

 

You're right. Here's the horrible damage it does. This is the inside of the gas tank of my old Corvette that has nothing but E10 for at least 20 years. The gas you see was over two years old when the pic was taken.

 

Thanks for posting the full report. I started this thread after reading a news article about the report. The report states that Top Tier gas results in "nineteen times less" carbon deposits, etc.... I have no idea what "nineteen times less" actually means. Is it one nineteenth? Is it trying to say that Non-Top Tier is nineteen times more?

 

What it means that even with '19/19ths' carbon deposits, the impact on performance of the car and mileage is minimal even under laboratory conditions.

Classic tempest in a tea pot.

 

>I think any carburettor issues should be in a separate thread or - better - another forum, as S-Types do not have such.

Sure, understood, but if that was in reply to my message, the note about carburetors was just an add on. I was really interested in how ethanol in fuel changes things.
================================================
Jaguar - it's not an automobile, it's a Motorcar
2015 JCNA National Slalom Champion Class M
Current: '08 S-Type 4.2 "Satin Edition" (250.06 whp / 259.67 torque)
Past: '05 X-Type 3.0/auto Jaguar Racing Green

 

It's been well and truly beaten to death far too many times. Out of frustration with the sky-is-falling crowd, several years ago I went out to the garage and snapped the picture posted above.