Premium Gas: Better Mileage & More Accurate Computer?

TeryT

TeryT

New member
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 . . .
 
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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
 
benk777 said:
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
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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/showthread.php?s=&threadid=12938&highlight=Iowa4runner


TeryT said:
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 . . .
Click to expand...
 
Update to trip

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.
 
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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.
 
CGY_LTD_V8 said:
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.
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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.
 
CGY_LTD_V8 said:
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.
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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.
 
TeryT said:
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.
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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 :)
 
CGY_LTD_V8 said:
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 :)
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WOW - using a particular octane will make me a happy camper!? And I thought new house siding was going to do that! LOL

Actually I'm just an over-analytical. Since I tow a lot, gas costs me big time. If I really thought it made a real difference when towing, I would certainly go for it!
 
I just completed a 3500 mile round trip from CO to NY to tow my 1959 Land Rover back to her new home. :) Since I had no driveshafts in the Rover yet, I just used a tow bar instead of a trailer. The Rover weighs about 3K lbs.

My first tank I forgot to put higher octane in the tank and filled up with my normal 87 regular unleaded. I got 13.5 mpg and had no problems. Then I remembered the recommendations in the manual and used 89 octane and got the exact same mileage. Since I had to fill up so often over the 1700 mile return trip I also tried a tank of 94 octane and got 14 mpg.

So, long story made short, octane of the fuel had basically zero effect towing a relatively light load. The 4Runner did great the whole way, plenty of power, no problems at all.
 
for a v6 engine is it ookay for me to normally fill up regular 87, but once every two to three weeks fill up premium? will my engine get spoiled?
 
for a v6 engine is it ookay for me to normally fill up regular 87, but once every two to three weeks fill up premium? will my engine get spoiled?
 
iFORCE said:
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.
Click to expand...

If you're running under similar conditions to my test, then any difference you perceive is not due to octane...
 
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