Deposits are another matter. 87 makes shiny black carbon deposits, at least on old 6 volt ignition. 87 will run exactly 20 minutes in our 8N Ford, not much longer in our v4 wisconsin forklift. Top off 1/2 tank with 91, go 40 min. Get to straight premium and they'll go for months. I read an article in Trailer Boating Magazine by a petroleum engineer who said premium is refined differently and doesn't leave these deposits, which are bad for 2 strokes. He said some 89 is good and some is just a blend. I can only use 91 in my business. 12V stuff is better, and electronic ign run fine on 87. This is what did the deed to the F800. Other than my pickup, I am afraid of regular- even those 75 gallon fillups don't tempt me! Maybe the pinging stops when the deposits burn off. ( kidding). I think these deposits are not a problem in modern things that run hot enough.

 

The biggest problem is that higher octane fuel in our low compression engines doesn't burn completely Therefore it carbons up the 02 sensors which insulates them from reading properly.This situation can lead to lower fuel mileage because of their readings fed back to the pcm.
Also Somewhere I read an article that the catalytic converter can become clogged over long periods of time of use with high octane.

Rich

 

interesting. That would account for the strong language.

 

If 87 octane doesn't run PREMO in your V10, something's wrong.

I've run 87 only in all my modulars. I ran 93 in my '96 t-bird for a while, found that throttle-response and other cold-behavior was not right.

With that V10 "pinging" you might want to check the dust cover on the bellhousing (if it's automatic) and all the exhaust heat shields. We've had lots of threads in the V10 forum about "Pinging" and how a lot of it is the dust cover or heat shields.

I run 87, with 10% Ethanol, and have NO PROBLEMS WHATSOEVER. I also don't notice any dimished power over 100% gas, drivability, MPG or anything else wrong with 10% ethanol (your milage may vary - literally).

But yeah, running higher octane than you need WILL lead to problems down the road, unless you drive like me. That is, I blow the carbon off the piston tops regularly letting the thing rev all the way out at WOT

 

Krewat - I'm glad you flog your engine that way and it doesn't come apart. Makes me feel better about letting mine run at 4000-4500 RPM on passes in Colorado (gotta love the sound when it's holding speed or slightly accelerating on a 7% grade at 7000') towing a small load with the throttle mashed. I still have diesel envy, but at least the V10 runs in ways my beloved Toyota Land Cruisers never will.

Steve

 

If you can't run it to red-line (or rev-limiter) and not blow it up, what's the point?

I took apart my FE360 that was in my '74 highboy. It had 150K+ miles on it, clean as a whistle in the combustion chambers. My machinist got real sarcastic when I wondered why it didn't have any carbon buildup. He said "The way you drive? There's no CHANCE any carbon is going to stick to anything". That motor was still going strong and had plenty of life left in it, and no copper showing on the bearings either. That motor only knew Castrol GTX all it's life.

Anyway, my point is, don't BABY the darn thing too much. That's when you get carbon buildup, pinging, etc.

The higher octane gas doesn't help that either.

 

The general rule is use gas of the octane that does not ping or that just barely or occasionally pings. Using higher octane will not hurt a modern engine> using really low octane like you might find in Mexico could hurt a high performance engine.

Most engines built now a days have computer spark controlled advance and will work within a reasonably wide range of octane, Such as 87 to 92. Some high performance engines will ping or knock(this is worse than ping) if running low octane fuel.

The usual reason a low compression engine pings is that over time, the cylinder heads have gotten deposits which increase the octane requirement.

So run the gas that seems to run best in your car. Running higher octane than needed will not hurt, but you will waste money if you don't need the octane. Use what the manual recommends or higher.

On my 94 F250 460 which I use to tow, I run 87 most of the time, 89 when towing in cool weather and flat land. Or I run 92 in hot weather and or hills. It will ping on 87 while towing in hot and hilly, but runs great without a tow. Most of my previous cars back thru about 1986 ran different octanes depending on time of the year due to heat.

One other thing... If your engine pings, use higher octane. If it still pings after using the highest octane you can find, then you have a mechanical problem such as carboned up heads, incorrect spark advance etc.

Good Luck,

Jim Henderson

 

Let's keep this about the V10, as the original poster has.

As to Ford's V10, they are setup for 87 octane. With my V10, with a knock sensor, higher octane gas doesn't get me anything more than 87 octane would, and it runs like crap with higher octane.