I just purchased a 1989 F-150, 4.9 L, 4-Speed manual w/OD, 4x4. What motor oil is recommended for this engine as far as viscosity etc. goes? Thank you.

 

I use 10W-30 year-round in my 4.9

 

People may disagree with me, but if it's not going to be freezing in your area I would use 20W-50

 

I have been running 10W-30 in my '92 4.9L since I drove it brand new off the lot. It runs as good today as the day I bought it.

 

Unless you see a lot of below zero F temps, a 10W front number is low enough for winter and in summer I would say a 15w front number is more robust (alwas want the thicker base oil, provided if flows well on cold start). As for the back number, that somewhat depends on the trucks condition. Do you have an oil pressure gauge? (I was getting 36 psi hot at 2000 rpm with a 30 back number and moved to a 10w40 and the pressure went up to 43 which is within spec--so I will be running 10w40 in the winter here in Detroit.) A 30 back number should suffice unless you are in extreme heat, then a 40 is better. If it is really hot the 20w50 probably is a good idea and I may go to that in the summer since my favorite oil, Valvoline Max Life is not avail in 15-40.

 

I used Mobil Delvac 15W-40 and had great results. Used less oil when I was abusing it (reving it a little too high) and went 5 to 8000 miles on an oil change. Original owner.

I am tempted to use it in the 5.4.

 

The newer engines are spec'ed out to a thinner oil. What does the manual recomment? Probably 5w something. I'd be reluctant to go beyond say a 10w30 on that without good reason. Check out the article:http://www.machinerylubrication.com/...up=Maintenance

 

I am tempted, but I wont.
I will stick to the factory recommended 5W-20.
I read that article and it gave me heartburn!

 

5w30/10w30 probably doesnt matter much. I use 5w30 in the winter for better flow, I change the oil every 2 months during winter because of short driving trips. I have 40psi hot idle on my truck with 5w30 so I could probably use it all year round. 10w30 has a closer spread so I just use 10w30 or 15w40 in the summer months.

 

A friend of mine is an ASE mechanic. He swears by using 5w30 year round will double the life of a motor because there is more oil flow and the thinner oil keeps the motor running cooler by pumping more oil thru the engine. I have heard this from other mechanics too. Its just a wee bit thin for my taste towing a 5000 pound trailer in 95 degree heat.

 

Well, actually I was thinking you might do well to run 10w30 so long as it is above zero F, but maybe I came off seeming more against it. 5w20 does give me heartburn and I would be inclined to go 5w30 or 10w30. If I were going to run 5w20, I would probably feel more comfortable with synthetic.

 

I swear by diesel rated dino 10w30. It quieted the piston slap in my dad's brand "C" 4.8L truck. The brand I use is Mystik JT-8, although Delo or Rotella would probably work as good.

The article on machinery lubrication even says at the bottom:

"The best protection against wear is probably a product that is a little thicker (such as SAE 10W-30 or 15W-40) and has more antiwear additives than the oils that support the warranty. The best oil for your vehicle depends on your driving habits, the age of your engine and the climate you drive in, but it is not necessarily the type of oil specified in the owner’s manual or stamped on the dipstick."