Thinking about gas prices and weather to use regular or premium fuel in my gasser RV

[BGMAC]

I was not doing much today and I started thinking about the difference in using regular or premium in my RV. It is written in other forums that the Ford V10 performance and mileage will improve on 93 octane vs 87. So I took to the calculator and using 300 miles of travel with regular being $4.22 and premium at $5.34 per gal. (That’s what it is around here) I also figured 8mpg on regular and 10mpg on premium.

Well, the cost of fuel would nearly be the same running premium or regular. So if you do get better mileage by 2 mpg you can run premium and get some of the other benefits it would provide,

I also played with the idea of using regular gas and adding octane booster. It is a little cheaper then using premium, but I’m not sure it’s worth the hassle.

Anyway, just thinking.

 

[Scooterfan]

If I don't feed my 8.1L Vortec 91 Octane she's not happy. Not worth the trouble IMHO

 

[Rich W.]

I‘d say try it and see. Having owned a few V10s, my guess would be that you wouldnt see much difference, if any. The only fuel issue I ever had was with ethanol. The ethanol blends definitely robbed power and reduced milage and these days its hard to find gas that doesnt have some percentange of ethanol in it. But other than that, using regular unleaded vs premium unleaded probably wont yield any noticable difference. Same thing with octane booster. The V10 is a fairly low compression motor (9.2:1) and doesn't have the capacity to take advantage of high octane.

 

[Buly]

If your engine is happy with the lower octane, and not knocking, leave it alone. Higher octane does not mean anything to a low compression engine. Just waste of money.
The opposite is true if you have a high compression engine. Low octane gas in it will make it knock and ruin the engine.

 

[GypsyR]

What Buly said. Also though it doesn't apply to a 6.8, on lesser low compression engines it has been found that high octane gas can actually cause lower performance. So you would be paying extra for less power. Point being that if you don't actually NEED Premium, don't use it. If you did need it, you'd likely already know.

 

[WinMin4]

Always used 87 octane so far so good - not worrying about mpg, more power the better.

 

[BGMAC]

Just got back from our trip to Orlando to see my daughter. I quickly realized why I left. Man was it hot!
Anyway, I used 87 octane this trip and got 6.7 mpg. Not too bad with the heavier RV towing my wife’s car and appliances on a trailer. Now that prices are dropping I may try premium just to see how things go.

 

[Rosy]

I would run whatever the manufacturer recommends. If it's tuned to run on 87, all 91 will do is empty your wallet faster.

 

[BGMAC]

I would run whatever the manufacturer recommends. If it's tuned to run on 87, all 91 will do is empty your wallet faster.

I understand what you mean, but engines aren’t really tuned to a particular octane much anymore. Now with computer control the engine will adjust to the conditions there in to give the best operation. This includes increased octane.

Some engines my have a higher compression which will require a higher octane. Lower compression engine can run lower octain, but may benefit from running higher octane when under stress due to timing advance.

 

[Rosy]

I understand what you mean, but engines aren’t really tuned to a particular octane much anymore. Now with computer control the engine will adjust to the conditions there in to give the best operation. This includes increased octane.

Some engines my have a higher compression which will require a higher octane. Lower compression engine can run lower octain, but may benefit from running higher octane when under stress due to timing advance.

I'll say I half agree with this. If your engine is tuned to run on 91, the computer will reduce power to avoid knock if you're running 87. But if it's tuned for 87, the computer can't magically pull more power out of thin air if you run 91.

 

[B52Bombardier1]

Octane is certainly important where indicated by the manufacturer. But I also try to only purchase "Top Tier" fuel for my vehicles. These are EPA-rated for a better fuel system detergent / cleanser package than the stuff that can be bought for ten cents a gallon cheaper.

I will run any brand of fuel when I must but if i have a choice, I stick with the Chevron, Exxon, Shell and Mobil brands if I can though there are other Top Tier rated fuels. Maybe I worry too much about fuel injector problems and carbon deposits in the combustion chamber, IDK. But this is what I do and my engines run well for very long periods of time so its pay them now or pay the mechanics later. I choose to pay a little more now.

Rick

 

[Rich W.]

I understand what you mean, but engines aren’t really tuned to a particular octane much anymore. Now with computer control the engine will adjust to the conditions there in to give the best operation. This includes increased octane.

Some engines my have a higher compression which will require a higher octane. Lower compression engine can run lower octain, but may benefit from running higher octane when under stress due to timing advance.

Thats why I say try it and see what happens. We all might learn something.

 

[Rosy]

Octane is certainly important where indicated by the manufacturer. But I also try to only purchase "Top Tier" fuel for my vehicles. These are EPA-rated for a better fuel system detergent / cleanser package than the stuff that can be bought for ten cents a gallon cheaper.

I will run any brand of fuel when I must but if i have a choice, I stick with the Chevron, Exxon, Shell and Mobil brands if I can though there are other Top Tier rated fuels. Maybe I worry too much about fuel injector problems and carbon deposits in the combustion chamber, IDK. But this is what I do and my engines run well for very long periods of time so its pay them now or pay the mechanics later. I choose to pay a little more now.

Rick

Shell is my first choice and Esso/Mobil/Exxon is my second. We only have 4 refineries here and I don't trust the other 2.

 

[mike n sue]

We Just finished a 4200 mile trip with our 450e v10 I am super impressed with the performance of that engine. we went from sea level in fl to 7000 feet in the mountains. Towing a Kia Soul on a Dolly we averaged 6.5 mpg all we used was 89 regular. Yes it was expensive, but we budgeted and saved, we are not getting any younger

 

["EZ"]

Have you guys ever watched the show on TV called Engine Masters? There is an episode where they used a big block Chevy motor on the dyno to find out if octane made any difference in HP. They also monitored fuel/air ratio all along the power curve. If I remember correctly they used 87 Octane as well as 91, 93, 116 Octane Sunoco race fuel and E85 (which is 85% alcohol). Know what they found? Their engine would run on 87 octane without knocking. It was making 500 (?) HP. After running the 87, 91, 93 and even the 116 octane fuels through it they overlayed the graphs on top of one another and there was virtually no difference in any of them! The HP didn't fluctuate more than about 2 HP no matter what fuel they ran. The E85 alcohol blend boosted the HP about 50 (?) extra HP because of all the extra available oxygen in the fuel. But obviously your engine has to be changed over to all the equipment necessary to run E85.

Moral of the story? If your engine will run good on 87 and not knock, then you are wasting your money on using any of the higher octane and more expensive fuels. Obviously if your engine requires 91 octane to not knock you should stay away from 87 but again you are wasting your money buying any higher octane fuel unless you want to switch to E85 but then you have availability issues to deal with.

 

[Rosy]

Have you guys ever watched the show on TV called Engine Masters? There is an episode where they used a big block Chevy motor on the dyno to find out if octane made any difference in HP. They also monitored fuel/air ratio all along the power curve. If I remember correctly they used 87 Octane as well as 91, 93, 116 Octane Sunoco race fuel and E85 (which is 85% alcohol). Know what they found? Their engine would run on 87 octane without knocking. It was making 500 (?) HP. After running the 87, 91, 93 and even the 116 octane fuels through it they overlayed the graphs on top of one another and there was virtually no difference in any of them! The HP didn't fluctuate more than about 2 HP no matter what fuel they ran. The E85 alcohol blend boosted the HP about 50 (?) extra HP because of all the extra available oxygen in the fuel. But obviously your engine has to be changed over to all the equipment necessary to run E85.

Moral of the story? If your engine will run good on 87 and not knock, then you are wasting your money on using any of the higher octane and more expensive fuels. Obviously if your engine requires 91 octane to not knock you should stay away from 87 but again you are wasting your money buying any higher octane fuel unless you want to switch to E85 but then you have availability issues to deal with.

I assume they were running the engine flat out at full throttle? I know that's a stupid question but I watched a very biased and unscientific show one time where they idled a Civic at 10 mph on both 87 and 91 octane to prove that advertising premium means oil companies are evil, or something.

 

[TheLooks]

How about an acceleration curve? How will it respond from low rpms to ramp up for that big hill? Fuel mileage while doing so?

 

["EZ"]

I assume they were running the engine flat out at full throttle? I know that's a stupid question but I watched a very biased and unscientific show one time where they idled a Civic at 10 mph on both 87 and 91 octane to prove that advertising premium means oil companies are evil, or something.

No, they start the pull at about 2500 RPM and run it up through the red line, which on this engine was about 7000 RPM. No matter which fuel was used the graph looked almost identical every time.

 

[Rich W.]

A. Fuel mileage will drop when you open it up and put some demand on it no matter what fuel you are running.
B. As long as it isnt pinging you have enough octane.

So, if it works on 87 octane there is no benefit to running more expensive fuels. If it pings under load, then yes, make an adjustment.

 

[FL-JOE]

A few months ago we took a motorcycle trip from our leased lot in Florida to Austin TX. About 50 miles outside of Austin I stopped at a rural Shell station and filled up with 93 octane. The next day I started having all kinds of issues with high idle and the bike not running right. Dealer determined it was old fuel. He said they had several come in recently with the same bad fuel issue because lower traffic stations were not selling their expensive high octane fuel and it was sitting for a long time in the tanks.

For the rest of the trip I used 87 octane and added octane booster. Even though my manual says I should run 91 or higher the bike ran great. I'm now back to using Shell 93 octane but only at stations that are high volume.