low87, med91,high93 octane

kc8kix · 12-19-2018, 04:18 PM

When we purchased our new winnebago vista, we were told to run medium grade gas even though the manual calls for 87octane. I was told by the person giving us the walk around that they have had better luck running a med91 octane fuel. At 40 to 60 cents a gallon difference when filling 85 gallons that comes to a big difference after awhile. My previous motorhome ran just fine on 87octane, with the same V10 engine. I swear that I got better mileage with 87. What are your feelings on the subject.

carlwatson · 12-19-2018, 05:06 PM

Quote:

Originally Posted by kc8kix

When we purchased our new winnebago vista, we were told to run medium grade gas even though the manual calls for 87octane. I was told by the person giving us the walk around that they have had better luck running a med91 octane fuel. At 40 to 60 cents a gallon difference when filling 85 gallons that comes to a big difference after awhile. My previous motorhome ran just fine on 87octane, with the same V10 engine. I swear that I got better mileage with 87. What are your feelings on the subject.

I saw no difference in any of the ethanol added fuels however i did see a 3+ mile per gallon using the non ethanol fuel after running several 75 gallon tanks through my chieftain 33 with the V10. I also found running the house AC with the generator (5kw) instead of the engine driven ac to be a fuel savings. At 65 mph I am over 9 mpg's pulling our boat.18ft.

SarahW · 12-19-2018, 06:23 PM

I feel that Ford's recommendation is good enough for me.

Podivin · 12-19-2018, 06:35 PM

Quote:

Originally Posted by SarahW

I feel that Ford's recommendation is good enough for me.

I'm with Sarah, do what the manual says to do.

akeagle · 12-20-2018, 12:57 AM

I too agree with Sara. Over the years I've heard and read many times to disregard the advice from "experts" to run premium fuel, even just periodically, in an engine designed to run on regular. There is simply nothing to be gained - except lightening your wallet by unnecessarily spending more money.

**ThomB** · 12-20-2018, 06:11 AM

If the difference was like in the "old days" where mid-grade was $0.10 more and premium was $0.20 more than regular than maybe I'd try running a couple tanks through to see if there is any difference but when the difference $0.50-0.80 no thanks.

thompwil · 12-20-2018, 07:38 AM

The older I get the better I was. I searched one of my old posts for something and replied to it instead of this post, oh well...

FWIW I started using 89 octane this past Summer. The cost of 91 or 92 is just too crazy here in PA for an experiment, though I may try a couple tanks next month as we head to the SW cost permitting. No increase in fuel mileage was seen though I did notice a "seat of the pants" improvement in engine smoothness, nothing I can quantify with data, just seems to run a bit better. Perhaps a placebo, but the Mrs. noticed it too.

From the Ford manual;
Tells you it's designed to run on 87 then tells you it's recommended to use 91. Go figure.

Ray,IN · 12-26-2018, 06:00 PM

Quote:

Originally Posted by thompwil

The older I get the better I was. I searched one of my old posts for something and replied to it instead of this post, oh well...

FWIW I started using 89 octane this past Summer. The cost of 91 or 92 is just too crazy here in PA for an experiment, though I may try a couple tanks next month as we head to the SW cost permitting. No increase in fuel mileage was seen though I did notice a "seat of the pants" improvement in engine smoothness, nothing I can quantify with data, just seems to run a bit better. Perhaps a placebo, but the Mrs. noticed it too.

From the Ford manual;
Tells you it's designed to run on 87 then tells you it's recommended to use 91. Go figure.

That's the bottom line, IMO it's designed to run on 87 per EPA standards, but runs better on 91 under actual conditions is what the Ford owners manual is saying without running afoul of EPA regulators.

BigDan1 · 12-26-2018, 06:01 PM

As any OBD II. Engine , when you run on 91 octane , the ECM will give more timing advance , knock sensors Permitting,
Gas mileage different ? Negligible , but seat of the pants ( throttle response) should be better

cshodges · 12-26-2018, 08:15 PM

If an engine was designed for 87, the manual will say "requires 87" and there's no point in running anything higher. You actually have less energy density with higher octane fuel. Your engine will not be able to take advantage of the higher octane, and it's wasted money.

If an engine was designed for higher octane, it may say "recommend 91, require 87" or "requires 91." In these cases, the engine was designed for higher octane rates (probably higher compression, etc). If it requires 91, you should run that. If it recommends 91, you should consider that -- in this case the engine will make more power and run better on 91, but is able to retard timing if it detects a lower octane to prevent knocking and engine damage. It will not have quite as much power, which you may or may not notice.

What is important is to use quality, name-brand gas that keeps your engine running clean.

Ret.LEO · 12-27-2018, 04:19 PM

Here in West Central IL our "mid grade" is actual good old fashioned gas. Usually .20 cents a gallon more. I gladly pay that. Proven better gas mileage, does not attract moisture like corn syrup does.
Illinois will post on the pumps which pump has ethanol. In Missouri they don't have to as it all has corn syrup added.

cj_calva · 12-31-2018, 06:02 AM

Hi
Grown up in the automotive r&d industry I let you know my opinion: Put the less expensive stuff in your tank as long as it is not E85.

Facts: 87 is less energy-rich than 91 and especially on grades while the engine turns in a lower gear on higher rpm, there is a certain difference. As the director of marketing of the 91-Octane-LLC I would tell you that driving up to Pikes Peak CO with the 91 gives you 30% more power than with the 87 on the last few miles. As the CFO of your Wallet-Protection-Enterprise I'll tell you that this is right but with the 87 you lose only 7-8 seconds (same fuel-consumption) and that's never 20 cent per gallon worth. Especially if, with 91, you do just one extra stop and have to re-accelerate. On a normal 5% grade over 10mls on sea level you will lose about 2 seconds (same consumption) with the 87. If you like to arrive at the same time means that you need more gas.

Ok, if you add all those seconds on all the grades you do, this gives quite a lot. And if you do this with all gas-driven cars, RVs, trucks etc, this give much more. That's why you don't get 87 in California and that's also why Ford recommend 91: Green responsibility. As for you: You lose the advantage of the 91 at the next intersection if the light is red instead of green.

Concerning the 95: this is good for your Ferrari if you want to reach 191mph instead of those poor 190 last time with the 91. 95 will be the right stuff for it. But in your Vista?

Conclusion: 87 is good, 91 is better, 95 is waisting money.

Some words concerning Ethanol (= alcohol, for fuel it's mostly corn based). Ethanol is less energy-rich than gasoline. Often, ethanol is added to gasoline due to price regulations etc. If it's in a range up to 10% you will not remark that (ok, the Ferrari reaches only 185mph). There are several European countries like Switzerland where those 10% of ethanol are even in the highest fuel quality. But E85, which is 85% ethanol, shows a significant increase of fuel consumption, especially on such heavy vehicles like RVs are. E85 is good for small city cars which are used for driving to work considering fuel consumption, price and green aspects.

Ret.LEO · 12-31-2018, 03:59 PM

The facts are though is that "pure gas" gets 3-4% better mpg than ethanol gas. Not my conclusion but facts stated by US Gov. studies. Pure gas attracts less moisture than ethanol gas.
I don't drive a Ferrari or drive like I'm driving a Ferrari, so the highest grade is non relevant.
The reason you can't find "pure gas" in Missouri is that the State financed and supported the numerous ethanol plants. We have two large ones within 60 miles of where I live.

Boils down to I am getting 3-5 percent better mileage with "pure gas" It attracts less moisture. It makes me feel good and I can afford to.
I don't skimp on what I use in my vehicle. I buy the best quality, freshest gas I can find from top tier brand name stations only. I'm the same way about oil, filters etc.
My last truck I sold was a 20 year old Toyota T-100 4X4 with 265,000+ miles. It still got 21MPG, used less than 1/2 qt between 3,000 mile oil changes. Early part of life I depended on Semi's, farm equipment to make my living, later my patrol cars. I took care of them the best possible way. P.M. is everything. Dad raised me with words of wisdom: Take care of your equipment and your equipment will take care of you" Dad was right