I recently bought a '97 f150 4X4 4.6 L with 42,000 miles. For the first few months I've only be able to get 230 to 245 miles out of a tank of gas (about 11 or 12 MPG). I decided to see if higher octane gas would make a difference on my last tank. So far I've 280 miles towing a boat for the last 50 and I still have 1/4 of a tank left. Should the gas make that big of a difference? If I take it in for a tune-up is there anything specific that I should ask them to do?

 

That one doesn't make much sense... Changing the octane should have almost no effect on your gas milage (and if it did it would be very minimal.) I'd check your gas milage again after finishing this tank of gas to see where you shoudl be, then go back to the 87 and check it again.

 

One question - you don't list your location - but what has the weather done? Has it been fairly cold the past few months and now recently warmed up? I can show you how drastically my fuel mileage differs depending on outside temperature. With the recent outbreak of spring, my fuel mileage has increased quite nicely.

 

Actually I live in Minneapolis so i've had the same weather as you. i just filled up and got 15.2 for my last tank. what ever the cause it just nice to get over 11 MPG since i guessing that the price of gas is going to go up in the very near furture.

 

In all likelyhood, its just the weather that has caused the increase in gas mileage then. I see it in all of my vehicles - but the trucks seem to get hit the hardest. Jan/Feb this year I was averaging 12.5 mpg on the '99 and 13 on the '97. Now that we have some warm weather , I'm up to 15 mpg on the '99 and 16 mpg on the 97, and my Jeep has also gone from 13 mpg in Jan/Feb to 17 mpg on its last fillup.

Amazing what spring can do!

 

In all honestly, while I usually pickup an extra mile per gallon during the spring aswell, I wouldn't think that the slightly warmer temperatures would give you 4.5 more miles per gallon. I've never seen the weather make more than a couple miles per gallon difference at the very most where I live (however it obviously doesnt get anywhere near as cold down here in Dallas either.) Regardless, I'm glad your now in the 15+ MPG range... That is much closer to what you should expect.

 

I also live in the Minneapolis area and the weather makes a big difference. A couple other things that affect mileage are:
1. Lower octane should usually give BETTER mileage, as refining the gas to a higher octane actually takes more energy out of it. That's why there is so much more energy for better mileage in diesel which is lower in octane than gasoline. Engine timing directly affects mileage. The knock sensor adjusts timing to maximize the mileage for the gas you are using without causing pinging, but if you are pulling a big load, higher octane sometimes gives better mileage, as low octane may cause the timing to be cut back so far to prevent ping that mileage is bad. Note higher octane can give better mileage in a properly tuned and jetted carburated engine with no knock sensor to automatically optimize timing for varius fuels.
2. The 10% Ethanol in the gas will reduce mileage a few percent, as there is less energy in ethanol than in gas. If you bought your premium at one of the state's few ethanol-free premium pumps (it's pricy, but some collector vehicles and boats need it) - the mileage would improve. The E-85 gas that some stations have (notably area Holiday stations) that is really high octane 85% ethanol (only for nearly new vehicles that have the E85 decal on the gas door) will get terrible mileage due to the lesser energy in the ethanol, but it is a renewable resource that gets us less dependent on foreign oil, and it allows the timing to advance significantly more giving more acceleration.
3. Strong tail winds and headwinds make a big difference too.
4. If you bought your premium out of state, you likely didn't get the ethanol in it, thus boosting mileage.
Dave

 

STX, were not talking a slight difference here. Two weeks ago we were stuck with temps not going much over 10 degrees F for highs, with below zero every night. The last week brought temps in the 50's and 60's and lows in the 30's and 40's. When it is as cold as it was a few weeks ago, even gas sipping cars turn into fuel hogs. My other car which gets 30+mpg the rest of the year will get around 22 for the Dec-Jan-Feb months because of the cold weather.

Stantd1 is right on with the comment that if you bought your gas out of state or non-oxy premium (for an arm and a leg), you would get better fuel mileage. the 10% ethanol blend will result in about a 3-5% drop in fuel economy versus straight gasoline. For those who don't know, Minnesota requires all gasoline sold in the state to be 10% ethanol as a subsidy for the corn famers.

 

thans fo the info. now that i think about it, it was really windy on the trip down (i was in Iowa). but i thought that Iowa has ethanol in all of it's gas also.

So lower octane gas should get better millage? i never knew that. so will the higher octane give you more power? if not what is the reason for it?

ryan

 

I always get more mileage from higher octane in my vehicles too. I have never heard of lower octane giving better mileage???
To me it seems that the higher octane is a more complete burn, thus giving better mileage. But price wise, it usually works out about the same.

 

Ah, a couple fellow minnesotans! You guys should swing by the other f150 site and join the MN chapter, we just got together last weekend and hit the autoshow, was a good time.

 

No, not all gas in Iowa has ethanol in it. Minnesota is the only state that requires it statewide.

Oftentimes you'll see the midgrade (89 or 90 octane) in Iowa priced lower than the low grade (87 octane). Thats because the midgrade has ethanol and the regular doesn't, and you actually see a small tax benefit from using the ethanol fuel.

 

I can say that when I switched from Eth. to regular fuel I did see 1mpg. difference and an increase in performance. Also on the plus side my truck has been running better and I have had to use less injector cleaner.
A lot of stations in my area don’t really differ much between the two for price, usually 1 cent. Last I knew there was a 5-cent tax break on Eth. the other 4 cents they put in their pocket.