What Octane Gas Do you Run?
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Freshman User
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What Octane Gas Do you Run?
I currently have been running 85 octane in my 93 460. It seems to do fine, no pinging as far as I can tell. I live in Colorado and 85 is the regular octane gas out here due to the higher elevation. I know the owners manual says to run 87, but if I'm not having any problems with 85 isn't it fine to use? Am I damaging any parts such as valve components or anything else? I would prefer to stick with 85 since 87 in my area is 30 cents more per gallon. What does everyone else run? Anybody from Colorado that could chime in? Thanks in advance!
Senior User
Joined: Apr 2014
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From: Skiatook, OK
Oklahoma for sure doesn't have the altitude one has to consider in Colorado, but I also run the cheap stuff with zero problem, even with ethanol in it. I am, however, headed for new sending units for the dual tank problem; some say ethanol is a contributor.
Lead Driver
Joined: Feb 2013
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From: Roseville, MN
Use the lowest octane rating you can without getting detonation (pinging).
Higher chamber pressure, like from higher compression or a turbo, will require higher octane to prevent detonation (all else equal). So lower pressure, like from thinner air, doesn't require as much octane.
Ethanol is a whole 'nother thing. It actually has much higher octane rating than most gas, so it's used to raise octane as well as corn prices, and that effect in an engine is good. But both ethanol and gasoline will dissolve different materials, and fuel systems that were designed for gasoline don't always do so well with ethanol.
Higher chamber pressure, like from higher compression or a turbo, will require higher octane to prevent detonation (all else equal). So lower pressure, like from thinner air, doesn't require as much octane.
Ethanol is a whole 'nother thing. It actually has much higher octane rating than most gas, so it's used to raise octane as well as corn prices, and that effect in an engine is good. But both ethanol and gasoline will dissolve different materials, and fuel systems that were designed for gasoline don't always do so well with ethanol.
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Freshman User
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Dumb question
Thanks for the replies. This is probably a dumb question but I'm quite the newbie and I am not totally sure what pinging actually sounds like, is it just a light knocking in the engine? Thanks!
Logistics Pro
Joined: Aug 2010
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From: Chillicothe
I run 87 in my 302. Tried 93 no ethanol once picked up about 1 mpg. Not worth it in trade off in price. Been thinking about running a tank of e85 through it for the cleaning effect it has bit don't want to risk it. I know my old blazer got crap mpg on it the one time I ran it. But after I did and went back to regular 87 mileage increased by 2 mpg and stayed there for a long time. I chalked it up to the high alcohol content cleaning the 175+k mile injectors out.
Lead Driver
Joined: Feb 2013
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From: Roseville, MN
It's kind of a rattling sound. Definitely not a heavy knock like big metal parts hitting each other. And it will happen most under heavy acceleration, and at lower rpm. If you let off the gas it will stop immediately.
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Cargo Master
Joined: Mar 2010
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From: Laramie, WY
I'm just north of you, in Laramie WY. I run 85 in my 9.2:1 351. Deto depends on a lot of variables. Ignition timing makes a big difference for starters. A rattle is a good description of the noise you want to avoid. Detonation can break a ring.
As for ethanol in fuel.. well, it's a bit of a damned if you do, damned if you don't solution to a serious pollution problem in many cities. I would not advise anyone to run e85 in one of these trucks. After somewhat extensive reading, I've concluded e5 fuel is a good thing. I'd rather see a little increase in food prices and a small drop in energy content of fuel, than have MTBE in my drinking water.
As for ethanol in fuel.. well, it's a bit of a damned if you do, damned if you don't solution to a serious pollution problem in many cities. I would not advise anyone to run e85 in one of these trucks. After somewhat extensive reading, I've concluded e5 fuel is a good thing. I'd rather see a little increase in food prices and a small drop in energy content of fuel, than have MTBE in my drinking water.
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Freshman User
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Thanks!
Appreciate all the replies, I will try hard to listen for a pinging sound an i'll go ahead and fill up with 87 to see if I notice a difference. Mudsport69 you mentioned running some e85 to clean the fuel system. I have never heard of that before but it sounds quite interesting. Let us know if you try it and what your experience is.
More Turbo
Joined: Oct 2006
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Mine is fine on 87 unless I'm towing heavy in warmer weather, then it will ping slightly. 91 eliminates that. In summer especially I try to keep one tank full of 91 in case I need to tow heavy. Otherwise I just run off the other tank with 87. I tried the timing bump on this truck, first 14 then 12. Would ping even with 91 so I went back to stock 10 setting. Also has 270K on original timing chain so that may be a factor. 92 460 4x4.
Senior User
Joined: Aug 2006
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Mine is fine on 87 unless I'm towing heavy in warmer weather, then it will ping slightly. 91 eliminates that. In summer especially I try to keep one tank full of 91 in case I need to tow heavy. Otherwise I just run off the other tank with 87. I tried the timing bump on this truck, first 14 then 12. Would ping even with 91 so I went back to stock 10 setting. Also has 270K on original timing chain so that may be a factor. 92 460 4x4.
Posting Guru
Joined: Jun 2003
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From: southwest michigan
91 or 93 here in SW Mich depending on what the station has. I moved the timing up to 12º - 12.5º several years ago and it worked fine on 87 (the lowest you can buy here) for a long time.
A while back, I started getting a knock under heavy throttle occasionally, and it seemed to get worse as the weather got colder, so I moved up to 89, then 91. I'm pretty sure the real culprit is a lean condition that I haven't been able to track down.
On a side note, I've run my Mountaineer on a 90/10 mix of 87 octane gasoline and diesel fuel, which would drop the octane rating down to a theoretical 80ish. Would only start to ping when I got up to around 12-15% diesel.
A while back, I started getting a knock under heavy throttle occasionally, and it seemed to get worse as the weather got colder, so I moved up to 89, then 91. I'm pretty sure the real culprit is a lean condition that I haven't been able to track down.
On a side note, I've run my Mountaineer on a 90/10 mix of 87 octane gasoline and diesel fuel, which would drop the octane rating down to a theoretical 80ish. Would only start to ping when I got up to around 12-15% diesel.
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