87 octane- why?
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Junior User
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From: northport NY
87 octane- why?
I finally got brave and tried some 89 octane. It ('03 F350 V10). runs smoother. Under certain conditions, it can lock up at 1100-1200rpm in od. before it shifts down, it will rattle a little bit, but its liveable, and it corrects itself. With 89, it never pings. Why does the manual say never to use anything but 87? If it runs bad, try another brand of 87. My brother has a Saturn, and if you use premium it will overadvance, make xs power and warp its little aluminum block. Does anything like this happen with the Ford? Even half 89 runs 100% better.
Lead Driver
Joined: May 2003
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From: Lyndonville, Vermont
The only reason to use a higher octane is if you have an engine that needs it. It has to do with compression ratio and engine design. Our trucks shouldn't ping on 87 Mine never does, that may be brand specific. Also I never heard of prem fuel having any neg effects in any engine I think thats a line of bull but I'd be willing to learn if anyone knows for sure.
Some winter fuels are junk so watch out for additives.
Dick
Some winter fuels are junk so watch out for additives.
Dick
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Junior User
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From: northport NY
We get gasahol (15%) here. Hess is worse than some others. The Saturn thing was on the level. They may have fixed it now. Apparantly they used the knock detector alone to limit advance.
Elder User
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From: Putnam Valley, New York
87 Octane----not Me !!!!
As far as I know, no manual states that you MUST use 87 octane. They state that you must use a MINIMUM of 87 octane---NOTHING LOWER.
I personally don't use anything lower than 89 in any of my vehicles. The lower the octane, the faster and hotter the combustion process is. Higher octane fuel cools down the combustion process. Do you think that the vehicle's manufacturer wants your engine to last forever ???? They want you to buy another one ASAP !!!
RON
I personally don't use anything lower than 89 in any of my vehicles. The lower the octane, the faster and hotter the combustion process is. Higher octane fuel cools down the combustion process. Do you think that the vehicle's manufacturer wants your engine to last forever ???? They want you to buy another one ASAP !!!
Last edited by Rongold; Feb 26, 2006 at 12:23 PM.
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Read Motor Trend, Truck Trend, Car & Driver, Automobile et cetera and you will learn that burning a higher octane fuel than what is recommended for your vehicle is a waste of your money. Be sure your engine is tuned up. If you still hear pinging from the engine, try a different brand of fuel. This is the fact, not opinion.
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Joined: Dec 2004
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From: Bensenville Illinois
I put 89 in my 05 F-350 with the V-10. The $800.00 fuel pump I had to put in on my 01 at 37000 miles wasn't worth putting the cheap gas in my new truck. The V-10 runs much better with the 89 than the cheap stuff.
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Fuel pumps sometimes fail early due to running the truck too low on fuel. The fuel keep the pump cool. In my 1999 V-10 the fuel pump went out at 86k after running 100 mph on the freeway with little fuel and then filling the tank completely. Wouldn't start fuel pump died right at the station two blocks from the dealer.
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From: Southern Colorado
In Colorado (at higher elevations), 'regular unleaded' is 85 octane. I've put nothing but 85 octane in my '99 V10 and it only slightly spark knocked one time in 95 degree heat, towing uphill. I will continue to run 85 octane until the cows come home. If it chronically knocked, I would run 87 here.
With a V10/crew/shortbed/4x4/4.30 gears, I get 12.9 MPG (max) on the highway, and 10.5-11.8 in town, depending on the temperature (summer/winter).
At 7000', I have 21% less power than someone at sea level, due to 21% less effective compression. So, a lower octane (anti-knock index) is just fine.
Steve
With a V10/crew/shortbed/4x4/4.30 gears, I get 12.9 MPG (max) on the highway, and 10.5-11.8 in town, depending on the temperature (summer/winter).
At 7000', I have 21% less power than someone at sea level, due to 21% less effective compression. So, a lower octane (anti-knock index) is just fine.
Steve
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From: Oakboro, NC
I can't remember where I heard this and cannot vouch for its veracity...
Because of the lower burn temperature, using higher octane than necessary can leave more carbon deposits from incomplete combustion. These deposits effectively increase the compression ratio and can be hot spots that would cause pinging if you go back to lower octane.
Because of the lower burn temperature, using higher octane than necessary can leave more carbon deposits from incomplete combustion. These deposits effectively increase the compression ratio and can be hot spots that would cause pinging if you go back to lower octane.
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From: northport NY
Mine says use 87, do not use 86, and if it runs bad to try another brand of 87- do not try premium. There is no mention of 88 or 89. Mine runs better & smoother with even 25% 89. Don't get me wrong, 87 runs fine and is all I ever used. If it hasn't strained in a while, it will rattle once and correct itself right away. I just don't like pinging- My other truck is a '79 (429, now + .060) that weighs 29,700 pounds. I only put premium in that & have the souvenier piston to remind me. They said it only needed regular gas, too.
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From: Lowell, MA
Actually, the 1999 Model Year Owners Guide, on page 172, states as follows. "Your vehicle is designed to use "Regular" unleaded gasoline with an (R+M)/2 octane rating of 87. We do not recommend gasolines labeled as "Regular" that are sold with octane ratings of 86 or lower for use in high altitude areas." The word "Minimum" is not there. However the word "Maximum" is implied.
Higer Octane fuel will burn slower and less efficiently in low compression ratio engines. It is designed to be harder to ignite by the heat generated in the compression cycle. I used to run 91 Octane about every other tank on my motorcycle. 87 was recommended. at about 50K it started preigniting all the time when I ran 87, so I kept it at 91 all the time. At about 70K I needed to do the valves. When I took the heads off, there was a layer of carbon about 1/16" all over the top of the pistons and in the combustion chamber. I scraped it all off and put it back together and it ran fine on 87 again. It seems that the carbon build up had increased my compression ratio so I needed the high octane. I think the carbon build up was caused by using the High Octane in the first place.
Higer Octane fuel will burn slower and less efficiently in low compression ratio engines. It is designed to be harder to ignite by the heat generated in the compression cycle. I used to run 91 Octane about every other tank on my motorcycle. 87 was recommended. at about 50K it started preigniting all the time when I ran 87, so I kept it at 91 all the time. At about 70K I needed to do the valves. When I took the heads off, there was a layer of carbon about 1/16" all over the top of the pistons and in the combustion chamber. I scraped it all off and put it back together and it ran fine on 87 again. It seems that the carbon build up had increased my compression ratio so I needed the high octane. I think the carbon build up was caused by using the High Octane in the first place.
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It was said before, higher octane with higher compression. Octane is a measure of the fuel's resistance to detonation. With higher compression engines, you will often suffer from pre-ignition with lower octane fuels. This is where the combination of heat and compression cause the fuel to detonate prior to reaching the top of the compression stroke. The knocking you would hear is the effect of the cylinder igniting ahead of schedule and prior to spark.
When utilizing higher octanes in a lower compression motor, you are generally just wasting money. The engine is designed to ignite at the top of the stroke without preignition, higher octane fuels won't change this. It is possible for carbon buildup to cause slightly higher compression causing an engine to knock over time, I have seen a few vehicles that like higher octane fuel as they get older. It should not normally be necessary.
Tune up would be my first approach to solving the pre-ignition problem.
When utilizing higher octanes in a lower compression motor, you are generally just wasting money. The engine is designed to ignite at the top of the stroke without preignition, higher octane fuels won't change this. It is possible for carbon buildup to cause slightly higher compression causing an engine to knock over time, I have seen a few vehicles that like higher octane fuel as they get older. It should not normally be necessary.
Tune up would be my first approach to solving the pre-ignition problem.