85 octane ok?
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Junior User
Joined: Nov 2009
Posts: 52
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From: Colorado
85 octane ok?
I have a 94 F250/460 in Colorado. Out here regular gas is 85 octane. I use it all the time with only minor pinging on initial acceleration and pulling steep hills. First question, I know a minimum of 87 octane is required by the owners manual, but is 85 ok if I can live with a little pinging? And second, will advancing my timing up from 10 to 13 or 14 help with the pinging? Thx
Elder User
Joined: Dec 2004
Posts: 742
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From: Eastern Iowa
Actually, advancing the timing will make it ping worse, since pinging is actually caused by pre-detonation. Your best bet is just to buy the correct fuel, or amend the cheaper grade fuel with an octane booster, whichever is cheapest. Also, something that can make that particular engine more prone to ping is a clogged EGR valve. Clean that out, or replace it first, and see if that doesen't fix the problem. 85 octane is awfully low octane though. Our lowest grade straight gas here is 87, and the ethanol blend(cheapest) is 89. No pinging with 89 octane, but at 10% ethanol, your mileage suffers a little bit.
Fleet Mechanic
Joined: May 2005
Posts: 1,575
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From: Puyallup, WA
The higher you go in altitude the less the octane rating has to be for the same engine design. 85 octane at altitude is the same from a engines perspective as 87 is at sea level
All three of my 1990 460's perform exactly as yours does, except mine are running on 87 octane at sea level. They like 89 octane better
You could drop the initial timing back to 4 degrees and see how your engine performs if the pinging bothersom.
David
All three of my 1990 460's perform exactly as yours does, except mine are running on 87 octane at sea level. They like 89 octane better
You could drop the initial timing back to 4 degrees and see how your engine performs if the pinging bothersom.
David
Post Fiend
Joined: Mar 2004
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From: Union, Washington
Listen to dmanlyr, he is telling you the truth.
Elder User
Joined: Dec 2004
Posts: 742
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From: Eastern Iowa
Well, that makes sense. Because I've never even seen such low octane gas here. And my elevation is a whole 650 ft ASL. As far as the octane boosters go, aren't they just alcohol? Alcohol does increase the octane rating of gasoline.
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Post Fiend
Joined: Mar 2004
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From: Union, Washington
Where in the hell in Colorado is the anywhere close to as low as 650 ft?
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Postmaster
Joined: Mar 2001
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From: So Cal
I have a 94 F250 460. I use it tow my 8000# trailer.
For around town in the lowlands I run 87 since that is the lowest we have. WIthout the trailer I get no pinging. If I tow in hot weather or mountains it will ping with 87 so I go to 89.
I have dual tanks. One tank holds el cheapo gas, usually 87 and the other has 89 to 91 depending on what I can get. If I start to ping, I switch tanks. Most of the time I just run on the 87 with the trailer.
You can boost octane by adding some premium to a lower octane gas. KInd of a 1 to 1 boost. For example 1/2 87 plus 1/2 91 averages to about 89.
Just some thoughts.
Jim Henderson
For around town in the lowlands I run 87 since that is the lowest we have. WIthout the trailer I get no pinging. If I tow in hot weather or mountains it will ping with 87 so I go to 89.
I have dual tanks. One tank holds el cheapo gas, usually 87 and the other has 89 to 91 depending on what I can get. If I start to ping, I switch tanks. Most of the time I just run on the 87 with the trailer.
You can boost octane by adding some premium to a lower octane gas. KInd of a 1 to 1 boost. For example 1/2 87 plus 1/2 91 averages to about 89.
Just some thoughts.
Jim Henderson
Post Fiend
Joined: Mar 2004
Posts: 6,056
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From: Union, Washington
There is a way to stop the pinging when towing. Since your gas mileage is gonna be toast when towing anyway, just unplug the vacuum advance. It is a temporary fix at best but it does work.
My permanent fix was a distributor re-curve and a shorted vacuum advance curve. The stock mechanical advance curve is way to long as is the vacuum curve. Then my totals now are 36° total mechanical advance in at 3500 RPM and an additional 10° of vacuum advance on top of that. It works well for my 1984 F250 Super Duty with C6 and 4.10 rearend. With camper and any one of my trailers behind (one of the boats or either of the quad trailers). I am still getting about 10 mpg around town (when I drive it that is, as my 1999 Ranger with 4.0 V-6 does about 22 to 24 mpg) and 7 to 8.5 towing down the highway.
The recurve removed any octane worries as will as a mild tendency to have the temp creep up with long climbs (10+ miles) in plus 90° temps.
My permanent fix was a distributor re-curve and a shorted vacuum advance curve. The stock mechanical advance curve is way to long as is the vacuum curve. Then my totals now are 36° total mechanical advance in at 3500 RPM and an additional 10° of vacuum advance on top of that. It works well for my 1984 F250 Super Duty with C6 and 4.10 rearend. With camper and any one of my trailers behind (one of the boats or either of the quad trailers). I am still getting about 10 mpg around town (when I drive it that is, as my 1999 Ranger with 4.0 V-6 does about 22 to 24 mpg) and 7 to 8.5 towing down the highway.
The recurve removed any octane worries as will as a mild tendency to have the temp creep up with long climbs (10+ miles) in plus 90° temps.
Elder User
Joined: Dec 2004
Posts: 742
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From: Eastern Iowa
Nowhere. Which is exactly why I was surprised to hear about your low octane out there in the mountains. I had never heard of needing lower octane fuel at high altitude.
Post Fiend
Joined: Mar 2004
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From: Union, Washington
It is all very true.
New User
Joined: Aug 2010
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Hi all - I just bought a 2011 SD with the 6.2L gas engine. What would anyone recommend running in it as far as octane levels? Will run unloaded at times on hunting trips, or will be hauling a mid-size fishing boat. Thanks for any advice.
Postmaster
Joined: Mar 2001
Posts: 4,968
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From: So Cal
Yup high altitude means you can use lower octane, ORrrrr, in the old days you could re-jet the carb. Don't know if you can adjust the mixture on a fuel injected engine, I think you can.
My gramps who lived in Albuquerque re-jetted all his vehicles when he bought them.
Good Luck,
Jim Henderson
My gramps who lived in Albuquerque re-jetted all his vehicles when he bought them.
Good Luck,
Jim Henderson
Post Fiend
Joined: Mar 2004
Posts: 6,056
Likes: 8
From: Union, Washington
Yup high altitude means you can use lower octane, ORrrrr, in the old days you could re-jet the carb. Don't know if you can adjust the mixture on a fuel injected engine, I think you can.
My gramps who lived in Albuquerque re-jetted all his vehicles when he bought them.
Good Luck,
Jim Henderson
My gramps who lived in Albuquerque re-jetted all his vehicles when he bought them.
Good Luck,
Jim Henderson