gas and performance

[Ron G]

I was just wondering if anybody else has been having some performance issues with the gas were getting now?its probably time for decarb and new plugs but my engine seems like its lost a little power on the last 4 or 5 tanks of gas is it possible the gas is the problem?

 

[Bob_VT]

Re: gas and performance

I was told to use the mid grade gas. Low grade not good and high grade too many additives.

It also could be the warm weather having the effect on the engine.

 

[steelespike]

Re: gas and performance

In my opinion there is no mystery. Gas is gas don't listen to any gobble de goop about additives.Run your motor on the octane it is rated for.Running a properly tuned
motor on anything higher than it is rated for is a waste of money and probably gas.
One exception might be some motors rated for say 89 octane you may want to go with the next available number. If it seems not right at 87 octane fuel try 90. I think it is the next available number.

 

[JasonJ]

Re: gas and performance

Mine is running fine. I use 87 in my 36 year old Merc with no ill effects. On a side note I installed a water/fuel seperator last weekend and realized my original fuel line and fittings were too small. I replaced everything with new 3/8th hose and fittings, and gained about 4 mph and a few hundred rpms.

Also, the additives in gas are the same regardless of octane rating. As has already been said, you should use the lowest octane the engine is rated for. Anything higher is a waste.

 

[jtexas]

Re: gas and performance

Has your area recently changed to E-10?

If so there's a chance you could get some issues the first time you fill up, if you don't drain the tank first and maybe clean it out, if you have a big tank say 20-30 gallons with gas been in there awhile. Or if the station where you bought it didn't clean out their tanks properly for the first shipment.

JasonJ on the additives: you sure that's true across the board all brands? Just wondered cause shell would have ya believe otherwise based on their on-pump display ads. I also only use 87 octane.

[edit added aug 30 - I take it back, noticed yesterday shell doesn't say that anymore but they do have a fancy name for the 91 octane - "v-power" or something like that]

 

[JasonJ]

Re: gas and performance

I don't want to say for sure Jtexas, Its just what I have read and seen. Who knows now-a-days with these gas stations.

 

[waterinthefuel]

Re: gas and performance

I don't really know how much relevance this has to outboards, but when I was a kid I had a go cart. We ran the cheap gas through it and after a couple of years that sucker had a valve so stuck that we had to beat it with a mallet. My uncle (a small engine mechanice) said it was the cheap gas. We began using the 91 and the engine never looked back, and we never had problems after with our outboards (which we also ran on 91) nor with any lawnmower or ATV engine thereafter.

I run my Vino 125 on the stuff and I won't switch. The additives help keep the engine running clean. I honestly believe that. When we used to run cheap gas we had carb problems with other engines (before my time, I was told this by my father).

I run the cheap stuff in my car, but anything else gets the expensive stuff, well with one exception. I believe since the gas increase we began using the middle grade in our outboards with no ill effects.

I believe running the cheap stuff won't harm the engine, I just don't believe it will run at it's best. It's only my opinion. With the go cart engine exception, I've not noticed any difference between the regular and supreme as far as reliability in anything I personally owned.

 

[Terry Olson]

Re: gas and performance

I'm no expert - but with that said I've had some experience with high and low octane fuels and the problems using the wrong grade can create.

The octane rating is essentially the fuel's resistance to combustion. High compression engines use high octane fuels to prevent preignition. When you run high octane fuel in a vehicle rated for 87 octane you may have carbon buildup in the cylinders because of incomplete conbustion of the air / fuel charge.

I ran 91 octane in the only new vehicle I ever bought (rated for 87 octane). The result was carbon buildup in the cylinders and a series of "service engine" light related returns to the dealership where they found and explained the problem. If that was the only problem I'd had with that Chevrolet I wouldn't be driving Nissans today - but that's another story altogether.

Is the 2 stroke / 4 stroke comparision fair? I'm not sure. You'd think 2 strokes would be more prone to carbon buildup from the combustion of oil in the fuel anyway. Maybe someone who knows more about this can shed some light on the subject.

On a related note:

In my area (Minnesota) gas stations are mandated to sell oxygenated fuel during the winter months. You can buy non-oxygenated fuel at many stations and the pumps are marked "for off road use only" or something similar. Basically, you're not sopposed to run this in your street car and it's made available for use in small engines which aren't typically designed to run oxygenated fuel. That's a entirely different matter - but I think it contributes to the confusion about which fuel to use.

The Minnesota Street Rod Association (www.msra.com) maintains a list of stations selling non-oxy fuel because older fuel systems are degraded by oxygenated fuels. I go out of my way to get this fuel for my older small engines but again at the lowest octane rating necessary. The other thing to consider is that oxygenated fuels don't store well so seasonal equipment should probably only run non-oxy fuel.

My two cents worth anyway.

 

[pecheux]

Re: gas and performance

I find the smaller the motor the better gasoline it needs to run at it's peak performance.

Ran low & high octane gas in a Merc 115hp and saw no difference. But I can tell the difference in the 9.9hp Johnsn and the 15hp force. 89 octane seem to be what my motors like best.