I have read this thread with delight. I have had problems with some cars that have high compression ratios that knock when less than high octane gas is used.

I keep going back to the VVT and electronic spark adv/retard.

I remember reading a study one time that said that most folks would buy premium WHEN they had the extra money (good economy) because of a false sense that it cleaned out the engine - not because the car required premium.

Then again, I do have a few cars (older Buicks) that WILL knock if I don't run high test.

Robert

P.S. Noticed I used high octane, premium and high test just to confuse the point. LOL.

 

And that made my day!

 

I enjoyed it as well. I still like to call it high-test and watch the kids stare back at me in bewilderment....

 

I'm not commenting on the supercharged vehicles here but I use an old school receipt. 1/2 premium and 1/2 regular. I've never had issues with any engines and many I ran hard well over 100k that includes a C5. I don't know for sure but I figure 1/2 premium works like octane boost and boosts the regular gas octane up.

 

Save yourself time and trouble, just pick mid-grade. The pump automatically mixes gas equally from the regular and the hi-test super high premium octane tank for you.

 

This is for real? I always assumed they made a "Mid-grade" that was held in different tanks?

I do know of one Exxon (family owned) station here that caters to the smaller (towed) boat crowd that has a mid-grade that is ethanol free. It is more expensive than the high test.

 

Most do the blended method since it is allowed. There is a way in the US to check it (Not sure if Canada has the same). When you go to your local gas station look and see the filling ports on the pad. If there are three different color caps, then the station buys 89 pre-mixed. If there are only two colors, then the pump mixes it for you or the station only has two octane ratings. If the station has four or more octanes (some here actually do) the pump is mixing fuel for you to create the octane.

 

We have two tank and three tank filing station here too, but either way there's no benefit in doing a manual half-and-half mix.

The much revered Sunoco 260 of the '60s and '70s was drawn 100% from the high octane tank. The Sunoco 190 was 100% from the low octane tank. The 200, 210, 220, 240 etc. were mixed inside the pump in various ratios. That's what the selector dial on the side did.

 

Why is there no benefit to mixing? So using octane boost has no benefit either?

 

No benefit in making your own cocktail vs. the product dispensed by pressing the [89 Octane] button on the pump.

If you want to run mid-grade [89 Octane] and the pump only has 87 and 93, well then yes, mix your own. It's the same thing.

I'll let Mikey jump up and down over the debatable benefits of various additives sold by retailers to dump down the filler tube.....



Have fun with that.....

 

+1 on JOsworth's comments, but I'm curious as to what benefits you're expecting from either doing your own mix (vs. letting the pump do it for you), or from cans of additive?

If you're doing your own mix and the station sells (let's say) 87 and 91 AKI, a half tank of each will give you a net of around 89 AKI. Jaguar states that the car would like a diet of 91 AKI please, so you're already two points down. The only incentive to do that is to save a bit of money.

The octane boost in cans is a different animal. Many or most actually do nothing in terms of raising the octane level, the ones that do raise it require huge volumes to make much difference. When the can says 'raises octane by one point' it means that it increase octane by .1, not 1.0. This means that if you fill your tank with 87 and pour in a full can of additive, your fuel is now 87.1 AKI. Not cost effective.

On the other hand, many believe that the octane rating of gas/petrol is also tied to other attributes, most commonly 'engine cleaning' or 'more energy' or 'cleaner running' or, or, or. All of these are false.

Can I start ranting now please?

 

Mikey?????????????? Are you mellowing over time??? Wow, such reserve.
LOL

 

Would still put in the 93 octane, my daily driver car so it is not worth the potential consequences for 6-7 dollar difference over the lower grade. I have used 89 in a pinch before and never noticed any difference though.

 

Must be the laid back country livin' . You're not the first to ask what's happened.

 

When I was younger everyone talked about the Amoco 93 or 94 (?) being the "best" gas. As the Amocos went away it switched to BP. Now people seem to like buying Hess because it is made from USA oil more than other brands.

Oh, and this is funny, there were stories when I was in high school that actually mixing the lowest octane with the highest gave a octane HIGHER than the highest octane! Never made sense but people did it all the time.

Kinda like that story that says if you fill you ice trays with warm water they freeze quicker. Funny.

 

First time I've heard that.

From wikipedia:

The company has exploration and production operations in the United States, United Kingdom, Norway, Denmark, Russia, Equatorial Guinea, Algeria, Libya, Gabon, Egypt, Ghana, the Joint Development Area of Malaysia and Thailand, Indonesia, Thailand, Azerbaijan, Australia, Brazil, and St. Lucia.

Pretty much the same as every other oil company.

 

I appreciate the explanation and I think how calm you explained it (seems you have a rep here?)? lol

I thought that mixing the different levels would bring the level up to 91.

 

For the record I've only put premium in the Jag to date.

I do know that you can use lower octane and the knock sensors will decrease power in order to reduce detonation. I think it retards the timing so that you don't damage the motor.

 

another thing people dont realize (it may or may not have been mentioned in the past 7 pages)

using lower octane than recommended also kinda reduces MPG.....which means you're getting worse fuel economy and filling up enough times to offset those few dollars you originally saved.

now does it sound worth it?

 

I didn't know that over there you have pumps that mix the grades.

Over in EU, different tanks for different grades. (even when I shifted on a station during college this was the case).

I've never heard of it being mixed at the point of delivery.

Learn something new every day.