I usually use 87 octane, but just filled up with 91 as we are towing this weekend & I want4ed to see how it would do with premium gas. Coming back from the gas station (a few miles highway) I was showing better than the usual trip computer readings. After this trip, I will report back on the exact findings.

The 91 octane was $3.09 while the 87 was 2.89. This is a 7% difference. I normally get less than 11 MPG average while towing using 87 octane. If I even get 12 MPG, it will be cost effective to use premium!

Also, some things I've been hearing on here make me wonder if the trip computer is tuned more for premium gas. (It usually over-reports by 7% - checked with mileage markers & GPS over many trips).

So stay tuned . . .

premium = good for driving with a load or a i-drive-a-sports-car foot.

regular = good for everyday truckin' around.

Isn't the need for higher octane levels solely based on the engine's compression ratio? I know some 4 cylinder Hondas, Acuras, and Toyotas take premium because they have compression ratios of 11:1 or higher. What is the compression ratio of the 4Runner? In my mind it should be very straight-forward: either it calls for premium or it doesn't.

Ben

Oh God not again!!!

The compression ratios is 10:1, right on the borderline.

seriously...

Actually the language in the manual says to use at least 87, but for best performance, use 91. I don't care much about compression ratios, but in performance & mileage.

For towing, I would highly suggest using higher octane gas. With high loads on the motor, higher octane gas will allow it to run more timing without detonation. This would increase towing performance and most definiltey save you some gas.

Towing may be a different story, but under normal driving conditions I found no difference in 87 vs. 91 with regard to ignition timing. And that's really the only way 91 can give you better results than 87. The energy content is the same.

To see the details of my octane test go here:

http://www.toyota-4runner.org/showth...ht=Iowa4runner

Well after our weekend towing trip (Scottsdale to Tucson), I'm a little dissappointed to say that it doesn't seem the premium gas made any real difference. At 1st I thought that I was getting significantly better mileage, but once the computer settled down & I refueled after about 150 miles, that wasn't the case. Towing MPG appears to still be a little below 11 on fairly level road.

I also did not realize any noticable difference in power.

At some point I may try premium while doing some steep acents, but for now I don't really see the point - it doesn't seem worth the extra 7% in cash (20 cents) a gallon.

BTW - To realize a 7% MPG gain at around 10 MPG (fairly normal towing MPG for the V8) would only be less than 1 MPG gain. And admittedly a 1 MPG difference is pretty hard to determine, given variations in road conditions, wind, load, A/C on or off, etc. Although I do think I would notice a MPG gain of over 1 MPG - which would then justify the cost of the higher octane.

Also, did not see any improvement in computer - it was still over-reporting.

I use premium out of habit more than anything. All of our other vehicles take premium fuel so its become habitual. I do lots of highway and the premium does "feel" better.

I challenge you to quantify those "feelings." I would love to see something solid that shows that buying the premium is worthwhile.

Again, the book says to use at least an 87 octane, but for maximum performance use premium - I just haven't seen a measurable difference.

I agree. It runs and accelerates smoother for some reason. whether it be a driver-added reason.. or performance related... Premium is all my truck drinks.

Big deal, it makes me feel better so I don't see what the problem is. I will use 91 and you can use 87. I'm happy, your happy