Hey guys, I have a 95 F150 regular cab, 4X4, 5 speed manual trans with a 3:55 rear. I am running 31 x 10.5 x 15 tires. No matter how easy I drive her I cant get better than 12 mpg. I have checked the tire pressure, changed the spark plugs (only broke one), the wires , the air filter, the breather filter, and the PCV valve. I had it checked for codes and all that came up was 411 and also check cylinder 1. Any ideas what I can do to get better mileage? Thanks for any help.

 

Actually, that mileage, with that combo, seems about right.

I have a '92, 300, 4x4, Ext. Cab, with 3.08, and 235 tires. Best I have ever gotten is 15.

You may want to try bumping the timing up to 12°BTDC or maybe 13 if it will handle it.

With your 4x4 and 31's, its pulling you into the 12's.

 

I'm running 31" x 10.5" and I've got a 3 on the tree standard in my '79 f100 2WD with the 4.9. I'm averaging about 17 l/100km, or almost 14 mpg. I've seen plenty of people *say* they're getting 20 mpg with the 4.9, but I have never seen any numbers to back that up. I think with the 4x4, that's pretty normal mpg.

 

Driving habits have a large influence on gas milage. If you rarely leave town and/or do a lot of short trips of only a few miles at a time then fuel milage will always be lower than average. That said a 4.9 or 5.0 should be able to achieve 15mpg on average IMO so check codes yourself and post up the results, and also check fuel pressure.

 

I've got same truck except she's 2 wheel and E.C.R.B. 3.83 in rear same tires I can easily go through the front tank in 150 miles and I think 120ish for the rear I don't think I have the 16/18 gal tanks like my owners manual says, I've always been told that our 4.9s weren't really known for mpg but they'll pull your house down

 

A friend checked for codes and the only code that came up was:
411 low idle
and check cylinder 1 (during the cylinder balance test)
Most of my driving is to work and back 12 miles each way

 

Thanks timbersteel, Ill try to check the timing and report back.

 

FYI, you shouldn't have a code for cylinder #1. Only MAF equipped vehicles can run the cylinder balance test.

'96 was the first and only year the 300 to be MAF/OBD2.

 

Those big tires are throwing off your speedo… you are driving farther than it shows on the odometer unless you've changed the speedo calibration.

 

My 88 2wd 3.08 gears gets 16 in town with M5OD. 89 Bronco 351W gets 11.

 

I wish that was the case Krooser, but the speedo matches the GPS and the odometer matches the mile sticks on the highway.

 

Thanks Timbersteel, that's a relief, I was a little worried the head gasket was bad. I'll bring that up to my friend, maybe he did the wrong test.
What about the Low Idle, the truck seems to idle and run pretty well.

 

When was the 411 code displayed?

KOEO or KOER?

KOEO 411 would display being its a stored code and that could have been a long time ago if you haven't removed the battery or disconnected the battery cables.

KOER 411 code would display if the PCM can't bring the idle within spec. 550-875 rpm is within range I believe, and if its below 550rpm, it may run, barely, if it does.

Generally, a low idle on a stock, unmolested engine and throttle body, is due to a sticking IAC valve. As long as the Throttle Stop Screw hasn't been tampered with, and is still locktited in place, then leave it be. Try cleaning the IAC valve with electronic cleaner or brake cleaner. Be sure and don't let any fluid get into the solenoid part. I use a Q-tip. Don't use carburetor cleaner. Don't clean the throttle plates with anything except soap and water. They have a sludge tolerant coating and is easily damaged with spray cleaners.

 

Your engine may not be fully warmed up to go into close loop mode(better MPG) driving that mileage.

My 89 F250 with 300/AOD 3.55 stock tires gives me a solid 14MPG. It takes about 7 to 9 miles to warm up(over night cold start) and ECU to go into close loop mode. I know this as I have a O2 monitor and fuel injector duty cycle monitor hooked up. And I can see when it goes into close loop.

 

Exactly.

I used to have a 92 Bronco with the 4.9. 15 mpg.

And that is interesting with the comparison to the 5.0

I have always wondered why we expect that 300/4.9 six to be an economy engine? Displacement is so close as to be negligible. Given the same vehicle, gearing/tires and driving conditions, I would expect very little difference between the two engine choices. Sure, there are design differences and completely different horsepower/torque curves, but at cruising speeds, you have the same displacement per mile and there is little reason to expect any difference in fuel economy with a properly turned and maintained engine.