Hi guys, ok I got a '81 F-100 for my Grade 12 year. that was 3 years ago... It has a Inline 6 cylinder 300 C.I. motor. Power steering. no AC. and its a 3speed Auto. From the beggining I have had really poor gas milage on it. It only has 90,000 Kilometers on it so thats like 50k miles I think. I have replaced the Carb on it, and the Radiator, it has a K&N air Filter, and the timing has been set quite a few times.. I get 11-14 MPG on it, which I would asume should be alot better at least around 20 or 22 no?.. ALso how much tourqe and power should these 300's put out stock? Mine feels like it doesnt have what it should have.. Ive heard guys can smoke there tires and do brake stands with these motors.. i can't.. I dont do this commonaly i just did it to see if the truck has a decent amoutn of power. and I dont think it does.. Also.. another question.. My father bought it at a Auction, and when we got it there was an airpump (I think its an air pump) that was seized up on it and there was no belt going to it.. all the hoses are still hooked up tho, but we have never had that air pump running.. Can this affect my performance much.. what does this airpump do?. please help, im going to school now and i cant afford the gas heh.

 

Sorry to say but 11-14 is quite typical. Some get better mileage, some get worse. For the power end, if you change to a lower gear in the rear end, you'll get a little more get up and go - but these engines are built for torque at low rpm's. Most of us that have hauled loads & know that the motor doesn't flich under load - and that's what the six does - low end grunt...

 

As for the air pump, that Ford's idea of a joke. The air pump is located on the front passanger side of the motor, right next to the alternator. A hose goes into a metal tube. The metal tube goes down to a chamber right before the cat (I call it a pre-cat). Fresh air mixes with the exhaust fumes to let the cat burn them better.
If you don't have it connected, it will screw with the emission readings at inspection time. If your state does not have a fume check, I would not worry about it not being hooked up.

Gas milage is different. IL6 usually get 12 - 14. Your bigger air filther should help some. Make sure you have good plugs & timing is set pretty good. Thanks about all the advice I can offer on that
Walter Danek

 

i have an 88 300/5 speed and i get right around 13 or so. the three speed probally contibutes to the lack of power. ive tried brake stands before and found out i had my foot on the brake to hard and smelt burnt clutch a little more then i wanted to make sure u dont have ur foot locked on the brake either.

 

My dad had an '81 up until about three years ago. it ran really well, but it certainly lacked the strength to do any of the performance stunts you mentioned.

The engine and truck, especially a truck of that vintage (even with low miles), is a great, reliable parts getter and hauler, but don't expect any substantial speed improvements.

If you want more hauling power, I agree that your three speed is limiting you. Though it probably really isn't limiting you for speed right now if you're running around with an unloaded bed.

You could try side-gapping the spark plugs (do a search for side gap/gapped/gapping spark plugs), make sure the carb is totally free of gummy residue, and a bunch of little stuff like that. Some people say reducing their vaccum lines really help on those older trucks.

But around town, if you make it to 13 to 15 MPG, then you're at its average working MPG. (oh yeah, you have to use kilometers, not miles, sorry 'bout that).

Lighter (which most times means smaller, but it can mean thinner) tires and wheels will reduce your rotational weight, which is always a big factor on any moving vehicle.

If it doesn't have leaks, synthetic oil, trans fluid and differential fluid will cause less internal fluid resistance. Some people report huge gains in distances-per-tankfull of gas with synthetic 0W-30, but i can almost assure you that while it may protect your engine better than any dinosaur oil, on that old of an engine it will find a way to leak out. I use Mobil 1 10W-30 since it's easy to find and rated well. The problem with this solution is the offset cost per oil change.

If you have it available up there, adding bottle of Chevron Techron before filling up the tank, then running it down to almost empty, has made a number of my cars run and idle noticeably better.

The airpump probably drained power from the engine, as do almost all emissions controls. If you have an air conditioner, take the belt off of it for a little more power and some extra fuel mileage.

Lastly, drive it like a grandmother. Trying to get going a little faster by revving out these low-RPM engines is an exercise in futility, and real diligent shifting will get you the best Miles Per Gallon.

 

Hey I agree the Chevron with Techron is great stuff but.....the techron is designed to work on injectors. A less expensive way would be good old dry gas and chenge out the tiny (Bad Ford Idea ) fuel filter in the carb.

Keep your tires inflated properly and drive with the wind not against it


Bob


84 Bronco I-6 (comfort)
78 Bronco 351M w/plow (power)
93 SHO (speed)

 

Actually the fact that Chevron Techron cleans the injectors and fuel system is an added benefit. When the stuff first came out it was like $16 a bottle and it represented a substantial move forward in engine cleaning as I recall.

Up until that point in time everyone had longed for a cleaner that would clean the burnt and built-up carbon out of the actual cylinders, then finally Techron was invented. It's now about $5.50 (US Dollars) a bottle, but it certainly isn't meant for injectors only.

err... now that I think about it...
The last time I looked at Pep Boys, there was a Chevron fuel additive with techron that was for injection systems, but there were also the original "Chevron Techron" bottles right besdie them.
Wal Mart carries only the good original Chevron Techron bottles as I recall.

Of course now that we're on the subject... another tip for tred99, if he's really caeful, is to search out the water-trickle method of cleaning out carbon. Pretty much anoyone with a carburator can easily do this method...

While working the throttle with your one hand, use a constant, but light, trickle of very clean water down into the carburator while the engine is running. Don't pour too much or the engine might seize (or worse). As this is going on one should, eventually, see a cloud of black smoke coming out of the exhaust pipe. This is carbon. Once the exhaust is relatively non-black, stop pouring water down it and let off the RPM's.

 

[updated:LAST EDITED ON 04-Feb-02 AT 09:59 PM (EST)]Canadians can and do use miles per gallon also. However their gallon is the equivilant of 5 US quarts, 11 MPG is not even 9 MPG (US). That is very bad. My 66 F100, 300 in 6 gets 18 mpg in town and 20+ at 70 mph on the freeway now (US) (I just completely rebuilt the engine after 268,000 miles. 3sp manual with od on 3.70:1 rear axle). Don't guess what is wrong. Take the time to actually analyze what your truck is doing (and what you are doing to your truck, I do drive like an old lady) you should be able to improve your fuel economy at least 50% from those numbers. Herman

 

Reading Herman's post got me thinking about other posts I've read on the I-6...

It seems that some feel that while driving it like a granny is essential for great fuel economy, keeping it in it's preferred torque range also really helps. (Herman's 3.70:1 read axle is what got me thinking about it.) I guess what some posters are saying is that keeping the RPM's too low on these engines is just as bad for fuel economy. I can't remember the exact RPM range to try to keep it in, but I believe it was right around 2000 RPM. It was stressed to the point (for newer I-6 owners) that even if this means keeping it in fourth instead of fifth gear on most highways is what you have to do, then so be it.

tred99 won't have the too-many-gears problem (he has just the right amount of gears... ok, maybe a creeper would be nice), but keepin' it between the extremes seems to be a good recommendation.

 

That makes some sense, I'm not sure what I'm turning at 60, but I've heard I should move up from my 2.73's for better mileage using 31" tires....hmmmm

 

ALso how much
>tourqe and power should these 300's put out stock? Mine
>feels like it doesnt have what it should have.. Ive heard
>guys can smoke there tires and do brake stands with these
>motors.. i can't..

Just to tell you, i can roast the 33x12.50 bfgoodrich tires on my truck with 3.08 posi rearend and an E4OD transmission (poured more white smoke than my friends Z28, black smoke is another story since its a chevy )..... although i wouldn't recomend doing it too often, since those tires go for $120 a pop

just my 2 cents, hope it gives a little perspective

 

[updated:LAST EDITED ON 11-Feb-02 AT 05:01 AM (EST)]I have a '95 f150 4x4 I6 300 with a 5" lift, 33x12.50R15 wheels, 3.55 gears behind a 5 spd., and even with the speedometer stock (never recalibrated) I still average 13 to 15 mpg. The 2k rpm range holds true for mine also. I haven't had any trouble with hp or torque, mine seems eager to spin the wheels, although I try to avoid it considering the angle of my driveshaft and stress to the u-joints (the trucks a short bed)
jonb