I have a 99 F250 V10 4x4. I'm currently using Valvoline 10W30. What oil weight and type do other V10 owners use?
Has anyone seen an increase in fuel mileage using synthetic oil?

 

I just picked mine up a month ago. The owner before me used a Volvo Marine 30w synthetic for 51,000 miles.
I changed it to 5w-30 Castrol Syntec.

There are pro's and con's to switching over to synthetic oil late in life.

I believe factory weight oil for the '99 was the same as the '00. 5w-30. If you have been using 10w-30 oil and show no adverse effects(engine noise) with it's use, then continue using it.

Personally I would not switch to synthetic with 50K plus miles. You'll have to listen to other's theory's and thoughts on that decision. Maybe I'll learn something new.

On Edit: I don't think you will notice much change if you decided to switch to synthetic.
What kind of mileage do you get?

Good luck,

Mike

 

i get 12 mpg around town if i keep my foot out of it and 16 mpg open-road.

 

Wow. I'm below 10 MPG. I'm running 285/75-16's though. 1 inch taller tire without calibrating the speedo. 4.30 gears. There is also a K&N FilterCharger on it.

I was going to put the stock air box on to see if I could sneak 1 more MPG out of it, but there is a piece missing.

MK

 

My tire size is 285/75 R16 and my gear ratio is 373. I have to keep a very light foot, no quick take offs, to get 12 MPG. It has gotten 7-9 MPG pulling a 5k lb camper.

 

I have 3.73's in my 99 crew-cab V-10, and I'm running 33x12.50x16.5's. I found my speedo is off .5 mile over 50 miles. I average 10 mpg rural driving, and 7.5 pulling an enclosed 24 foot car-hauler weighing around 8500 pounds.

There seems to be a distinct pattern with the V-10's, some average 12 and others average 10 mpg. My buddy has the identical truck to mine, and he averages 12 for roughly the same type of driving. He also pulls an enclosed trailer and averages 9 mpg. Wish I could figure out what the difference was....