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[quote=WanganKin;566862]It depends, if I am going HIGH altitude wheeling, I usually tend to put in low octane especially since there is not a lot of air up there anyway. That and with the 91 already in the tank the higher octane balances out the low octane.
Ok, I know I am ignorant: what is the reasoning behind going to where there is less air and being cool with gassing up with the low octane? Not being a smart-a, I really don't get it. Please don't flame me.
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From day one (over a year now) I have put 87 octane in it, and never had a single problem.
(After feeding my previous 1997 Jeep Grand Cherokee 89 for many years, whenever I put 87 in it, I had noticable "nocking"!)
I got a little nervous when I bought a 4,100 pound travel trailer, and hauled it through some of the Adarondack hills in Western Massachusetts - but even with 87, no knocks.
When ever I pull the trailer now, I put a tank of 93 in (to help keep the engine cool with the extra weight and summer heat), but then I switch right back to 87 with nothing in tow. After 2 months of this - absolutely no knocking. (To tell you the truth, I never noticed any difference on the engine temp gauge running either octane while towing either.)
Just turned 12,000 miles and except for being the trails at the Summit where I used high octane, I've exclusively used 87. No pings, no rattles, good mileage! 21 to 22 mpg at 68mph highway, 19 mpg city
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It depends, if I am going HIGH altitude wheeling, I usually tend to put in low octane especially since there is not a lot of air up there anyway. That and with the 91 already in the tank the higher octane balances out the low octane.
Ok, I know I am ignorant: what is the reasoning behind going to where there is less air and being cool with gassing up with the low octane? Not being a smart-a, I really don't get it. Please don't flame me.
My mentality about that is... well some facts... Air burns hotter than the Gas does... Running lean the exhaust tempatures would be higher... meaning the cylinder head temps would be higher also... which could lead to detonation aka pinging. If there is less air the ECU would automatically advance the timing and make adjustments to the fuel map and the amount of fuel being injected (TG for EFI...) and the car will run perfectly stoich (stoichiometric) unlike a Carb'd vehicle.
I figure since there is less air my car would naturally run rich... but again EFI will correct for this and reduce the fuel mixture down... If there is less fuel and less air..... mainly less air my chances of detonation possibly went down... So I figure why not squirt some 89 or something into my 91... Since there is already high octane in there it will balance out fine... plus again praise EFI for doing what it does best...
that is my theory behind it... but again even if you just ran low octane from day one... EFI will account for that you will just lack some/little performance...
Last edited by WanganKin : 08-23-2007 at 01:15 AM.
Your correct. At higher altitudes, the ECM will advance ignition timing and reduce fuel to maintain proper combustion and try to regain a little of the loss at altitude, but you will still be loosing HP the higher you go in a naturally aspirated engine.
DEWFPO (7,200 ft)
__________________ 2007 FJ, 5AT, Sun Fusion Yellow, CQ, UP, GY, RB, 2Q, EL, VS.
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I think I am going to do 1000miles at 91 (ny premium) and then 1000miles at 89 and see what's with it, if that will even tell me anything....
I have about 20K on my FJC and only run 87 and it runs ok. I make many runs between our home in Los Angeles to our 2nd home in AZ. On these trips I run just under 80mph on the open highway and get about 17mpg. The best mileage I have ever managed was 19mpg, but that was driving just 65mph. I ran two full tanks of 91 and I couldn’t tell any difference at all. But it’s really hard to tell when you have this California pumps that don’t allow you to fill to the stopper.
I own a small airplane and it has a 150hp Lycoming engine and it runs on either 100 aviation gas or 91 octane auto gas. I can tell a slight difference in performance, but it’s small. I usually run Av Gas in the airplane because they have a pump at the airport and it’s a lot safer than hauling gas to the hanger!!
I’m sure the FJC would enjoy the higher octane, but I just couldn’t tell any difference. If you have another FJC that is exactly the same configuration as yours, it would be really interesting to fill them and make a comparison on a simultaneous highway run. I would be interested to see the mpg difference.
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Last edited by Aviator_Guy : 08-31-2007 at 09:42 PM.
2007 FJ, 5AT, Sun Fusion Yellow, CQ, UP, GY, RB, 2Q, EL, VS.
Re: What grade gas do you run?
Re: What grade gas do you run?
Linear Mode
