Fuel ????

[Bob Denman]

With today's computerized engine management systems: if it'll burn... the engine will run on it just fine.
The generator is another matter.
Buy your fuel to protect that unit: it likely does not have the same safeguards in place!

[Baddad53]

Originally Posted by SuperD

Colorado did a "scientific" study that showed higher altitudes and less dense air reduced detonation in engines, this lead to reduced octane and 85 gas. There is no true study that confirms this, in fact it is very contradictory to what actually occurs in an engine at altitude. More evidence of government officials meddling in things they know NOTHING about!

Political comments are not allowed here.

[Baddad53]

Originally Posted by Joe-FL

On our trip out west this summer we found several states with 85 octane. In addition there were two states that had a separate nozzle offering "non alcohol" blend gasoline which was interesting.

We never entered California so I can't say what them folks are up to. Visited the high points in that state a few years ago and won't be back. Driving a diesel at the time and just remember the quality of diesel went down and the price jumped about .60 per gallon.

The price of fuel here is indeed high...but your quality statement is off base.

[16ACE27]

Originally Posted by Baddad53

Political comments are not allowed here.

Good thing his statement wasn't political then.

[Bob Denman]

Since I'm the "newbie" here: can someone define (or at least illustrate...) what constitutes a "Political" post?
I get the the whole "my side is right, and yours isn't!" part...
But what else gets us in trouble?

[99dart]

Originally Posted by Msturtz

Octane is a measurement of a gasoline's resistance to preignition or knock. Spark ignition engines rely on very precise ignition timing. Combustion occurs when the piston reaches TDC (Top Dead Center). Knock occurs when the fuel air mixture detonates by heat prior to TDC which is bad for the engine. Modern engines have knock sensors and will retard timing and other things to reduce knock. At high altitude the air is less dense and the higher octane isn't required because the computer also injects less fuel. All of this reduces the effective compression ratio of the engines thus reducing knock. The notable exception is turbocharged or supercharged engines that have above atmospheric intake pressure.

Right on. Good explanation.

[Chance]

I've purchased 85 Octane gasoline many times on trips out west in various motorhomes (rented and owned) and also personal cars, and have never noticed any signs of detonation.

As previously stated by others, ambient air is at less pressure, so when engine compresses it the maximum pressure in cylinders isn't as high. Of course that's only at full throttle because at partial throttle pressures can be the same or higher.

What is also very important is that air in the mountains isn't likely to get as hot as at sea level. While we see 100 F in Houston or Dallas every summer, temperatures in mountains at elevation are usually much cooler. Therefore at full throttle not only are maximum pressures lower, but maximum temperature before ignition is cooler also. That's why 85 Octane has been OK for me. I also rarely use full throttle to climb mountains, if at all.

I would buy 85 Octane again in mountains unless they were having a heat wave.




Regarding generator, we don't use it often since we stay in campgrounds with hookups. And in the mountains it's cool enough that A/C isn't needed, and dash air is adequate during day if needed at all. Anyway, if we run generator at all it would be a few minutes to power microwave or make coffee, and I don't think that's going to hurt it by building up carbon. Regarding carbon I'd worry more about other variables more than 85 vs 87 Octane.

[Joe-FL]

Originally Posted by Baddad53

The price of fuel here is indeed high...but your quality statement is off base.

That would be a matter of opinion. I was running a 2012 6.7 diesel at the time so it would burn b-5 to b-about anything. But the diesel prices run about .40 to .60 a gallon higher in California and you can't find anything but b-18 to b-20 which IMHO isn't the highest quality of diesel to burn. I'm basing this opinion on 3 years full time traveling in that diesel recording my mpg.

[axis earl]

Originally Posted by Halibut214

Huh? This makes eactly zero sense to me but am certainly open to hearing why.

I got a bit more of an explanation from the contact at a company called the Paint Department in Chino, CA. This is a full service business and has one of the largest RV painting facilities in the area. The tech I spoke to explained that the generators on our RVs are low compression in their engineering. High octane gasoline is blended for high compression engines that call for the high octane which generators do not. He also said that RV generators are made to run generally at 3600 RPMs. The high octane fuel causes the RV generator to actually run at lower RPMs which changes how it cycles and tells the little computer something different is going on and will end up shutting down the generator. I guess if you want to hear it from the author, you could call this business and ask to speak to "Chuck". As I said, I don't plan on putting anything other than regular grade fuel in mine anyway.

[Msturtz]

Originally Posted by axis earl

I got a bit more of an explanation from the contact at a company called the Paint Department in Chino, CA. This is a full service business and has one of the largest RV painting facilities in the area. The tech I spoke to explained that the generators on our RVs are low compression in their engineering. High octane gasoline is blended for high compression engines that call for the high octane which generators do not. He also said that RV generators are made to run generally at 3600 RPMs. The high octane fuel causes the RV generator to actually run at lower RPMs which changes how it cycles and tells the little computer something different is going on and will end up shutting down the generator. I guess if you want to hear it from the author, you could call this business and ask to speak to "Chuck". As I said, I don't plan on putting anything other than regular grade fuel in mine anyway.

In short no no no. The gasoline generators are governed to run at 3600 RPM to provide 60 Hz AC power. The frequency of AC power is directly related to the RPM of the generator and the windings. High Octane fuels resist knock or pre-ignition. You won't hurt the engine by running a high octane fuel in a small motor you will just waste money. That said you cannot use E85 fuels in small motors because that can corrode parts and has a lower energy content and can create other problems with lower HP.

[Laco]

True octane will not change the RPM's the engine governor or computer is set for. Also true higher octane fuel will only resist pre-ignition, or as we used to call it pinging. Since at higher altitudes there is less oxygen, the likelihood of pre-ignition is much less, hence a lower octane fuel run at higher altitudes will not damage anything. You don't need the higher octane at higher altitudes to resist pre-ignition since the possibility of pre-ignition is so low. Running a higher octane fuel in a lower compression engine will hurt nothing, will help nothing, only costs more. (I know some of the folks at the Paint Department in Chino, will have to ask them who thinks octane has a direct relationship to RPM's).

[SuperD]

Actually high octane in a low compression engine will hurt. High octane burns slower and the engine can't develop full power.

[wayneroe]

Originally Posted by SuperD

Are you sure it was 85 octane? Could it possibly have been E85? Two different animals.

I lived in Colorado Springs for a year (2004-2005). When I had been there a few weeks, I asked one of my co-workers why gas was 30 cents/gallon more than it had been in Illinois. He asked how much I was paying, I told him and he asked, "Where in the world are you buying your gas?" When I told him, he asked what octane I was using. I told him I was using 87 and he said, "No! Don't do that. You don't need it here. Use 85 octane." It was the same price as 87 octane every place else. Before trying that, I called the service department at a local dealer for my brand of car and he confirmed that 85 octane was all I needed there. I switched to 85 octane and experienced no degraded performance during the year. In fact, my gas mileage actually increased after I had been there a couple of months.

[Bob Denman]

And I thought it was only us bikers, who liked to argue about gasoline!
Just run what the owner's manual says to: you'll never hurt anything by following the "Rule-book"!

[captmetal]

if your worries about gas prices, probably should not have bought something with a 80 gal tank

[Bob Denman]

I couldn't have said it better...

[SuperD]

One of my good friends had an older BMW 7 series he had bought used. Very shortly after purchase the car started running poorly, he took it to three different shops and spent $2500 in repairs. My friend finally went to the BMW dealership, where he should have gone to begin with. The service manager asked him several questions about what had been done to the car, ask what kind of fuel he bought and he replied premium. The service guy stopped right there and said that's your problem, this engine was designed for regular. After my friend ran out the premium and put in regular the car ran just fine. Regular was 87 octane, premium was 91. Octane does make a difference.

[Buttonguy52]

I was told if you ask how many miles per gallon, don't buy one. Saying that our ACE averages about 9 miles per gallon. That's using the cruise control.

[Bob Denman]

Idle curiosity (and a desire to figure out your driving range...), will always end up making that question leak out into the conversations.

[Travelin' Texans]

Basically if you want/need regular unleaded then use that nozzle wherever you're filling up as it has been formulated for whatever geographical area you're in. If you want to spend more use blend or premium, it won't hurt a thing, an occasional fill with premium will help clean injectors.