May be I am getting senile, as my wife states, but my stock motor seems to run better on premium gas than the 87 grade regular. I think I was always told premium was a waste of money on a regular gas stock motor. Do I remember correctly or are there benefits in using the premium in the stock I6, 300.

Just wondering.

 

Very unlikely a stock engine in these trucks can benefit from anything beyond 87 octane. They had about 8:1 compression ratio and 87 octane is more than adequate for the little squeeze. The only way a stock engine could is if you have the timing advanced dramatically, or if it is badly carboned up. In either case correct the problem instead of buying expensive gas.

 

Hi Blu . I'm just downhill from you, E of Stuart. G2G time.
I've had vehicles that run and get better mileage with premium or higher octane. So much that the increase in mileage offsets the cost. With some of the problems I've had with ethanol, I've gone to E free premium in a couple of vehicles. Have you noticed that some stations in NC have signs on their pumps "may contain less than 10% ethanol" or "contains less than 10% ethanol"

PS: I don't remember if "senile" comes before or after "CRS"

 

You get used to this in forums like this, I guess, but this is a classic example of how asking in a forum can be worthless...

No criticism intended of any particular person or anything, this is just the way these things work...

Guy asks a question - should I use this or not?

First response says no, don't waste the money.

Very next response says yes.

WTF? How helpful is that?

 

I will put my 2 cents in.

On computer controlled cars and trucks, yes you can see an increase or decrease in performance and economy with different fuels. That's because the computer is constantly monitoring things, if it finds out it can advance the timing to take advantage of a better fuel, it will and it will do it automatically.

These old trucks can do the same thing IF, you go out and re-tune the engine manually when you go to the different fuel. But normally, if you do not plan and re-tune the engine, you will not notice much difference.

 

That's as helpful as I know how to be. The problem is that unless people post well-documented data we don't have anything to go on. Saying "seems to run better on premium gas than the 87 grade regular" is subjective and cannot be proven one way or the other. And saying "I've had ....." without data to back it up isn't definitive either. And when I say "data" I mean several back-to-back tanks with everything carefully logged.

But, what about me? I didn't quote any sources either. Truth be told I have none but a college class on the Internal Combustion Engine. That class taught that as long as an engine doesn't ping or detonate on a given fuel then there is nothing to be gained by running a higher octane fuel as the higher octane just makes the fuel harder to ignite.

And, then there's this from Popular Mechanics:

 

That's funny!

What is great about a forum is that you have a group of people with different points of view. In a facilitating environment it can help flesh out an appropriate answer. Peer review so to speak.

If you wait long enough a good answer will come out.see Franklin2 above.

 

Exactly! Because nothing is measured before and after so there is really nothing to compare, and a seat-of-the-pants feeling can be influenced by several things (including one's mind, i.e. stuff is imagined because one wants to imagine it being true).

After a while being here, you get an idea of who knows what they're talking about and who's blowing smoke up your azz. What you said is more in line with what I have learned, too... And, in my mind, is therefore generally accepted engine-operation principle and no substantiating documentation is necessary. Kinda like we don't ask for proof when somebody says water is wet.

The following response was 180° offset from yours but could also be true in certain circumstances (it depends).

Overall, though, on both sides, we don't have enough specific information about anything, so the entire conversation is pretty worthless IMHO.

Sometimes it can work out that way, yes, but only when one is dealing with some sort of hard factual data (and not opinions) that can be substantiated and replicated... I don't see it happening in this case because, again, we don't have any specific information, just a bunch of babbling....

 

I run 90+ in all my vehicles. But they get pretty much the same mpg with 87. I live on a farm and we have 90+ in a Co-Op tank so I just fill it with that. In my Ranger I get an average of 23.6 on 90+, that's the average of around 8 tanks I can't remember for sure. I wondered if I would get less and out of 2 tanks of Shell 87 I got an average of 23.2. But that is NOT definitive evidence because obviously you can't drive the same all the time. And that is in a 95 Ranger with a 2.3. I'm sure the difference(if any) varies from one vehicle/motor combo to another.

 

I've heard it said gas stations don't sell as much higher grade gas so it has a tendency to sit longer in the tanks and go sour.

On the other hand, Regular gas turns over more quickly and is thus likely to be fresh(er).

YMMV.

 

Cole - Your Ranger is EFI, and those systems can increase the MPG with higher octane. They have knock sensors and increase the timing until they get knock (or reach the limits of their table) and then reduce the timing to prevent knock. But some vehicles come from the factory set for 87 octane, meaning they won't increase the timing enough to get knock, and you can feed them 91 and see little, if any, gain.

On the other hand, if the vehicle came from Germany it will be set up to use 91 or even 92 octane and the MPG will go up with the better fuel. One way they do that is by increasing the compression ratio. For instance, MB's GLK 350 has a 12:1 compression ratio. That plus variable valve timing plus knock sensors lets them use the high octane fuel. Previously I had an ML 320 with a 10:1 compression ratio and I was extremely careful when refueling, bring the gas up to the top of the filler neck and keeping records on each tank. And I tried lower octane fuel to see what would happen and, sure enough, the MPG dropped. In fact, I could see the MPG drop with a certain brand of fuel - which shall remain nameless since I worked for them for 20 years.

Our trucks are different. Ford gave them 8.X compression ratio and set the timing at a reasonable value so they don't require more than 87 octane. They don't have knock sensors so even the ones with computers don't advance the timing until it knocks and then back it down. The computers work from a timing map that Ford put into them that ensures no knock with 87 octane. So you can give it higher octane but it won't take advantage of it.

 

It's my understanding that it's the ethanol that shortens the lifespan of gasoline, as it absorbs more moisture. If the premium is ethanol free, then it will last longer without getting stale.

So before I read your post, my thinking was leaning towards the premium might have been effectively "fresher".

Don't know if the OP was purchasing all gas at same station, or various ones, but none the less, fuel quality could factor in as well.

 

Where I live all grades are diluted with ethanol. You have to hunt for special stations to get "clear" (undiluted) gas.

 

Yeah I know, I wasn't sure when(or if) the 300s converted to EFI. I've never been around an I6 except my dad's Cummins haha. I've heard from some places that premium is supposed to burn cleaner and have less carbon buildup, not because of the octane but because of better quality ingredients in the rest of the fuel. Is this probably true or false? There are so many different opinions it's hard to tell what is right and wrong. And in reality my guess is it depends on what brand of gas it is.

 

You are right - it depends on the brand. Some put the same additive package in their 87 octane as they do 91. So in that case the 87 burns as clean as the 91. But not all do that. And the additive package makes a difference, for sure, as some packages are better than others.

A few years ago we had an Acura that developed a stumble when the engine was cold such that it would die at the end of the driveway going from Reverse to Drive. I consulted with the lead tech specialist at the petroleum company where I worked and he asked if I was using our gas. Duh! Sure. He then explained that I had a buildup in the intake that was absorbing fuel when the engine was cold. It was a known problem and they were changing the additive package to resolve it. But to fix my problem I should start running Chevron's gas because its additive wouldn't cause that buildup. And, for the first several tanks I should run a bottle of Techroline, which was their additive just in a bottle, to help clear out the deposit. Sure enough, after a few tanks the stumble gradually went away.