I have an '87 Ford E-250 4.9L inline six work van. I have a carpet cleaning machine that runs off of the van (PTO), so the van has to idle at a medium RPM while I'm on the job, probably around 2000 rpms. the motor was rebuilt 5 years ago, a ford authorized rebuild.
The past owner ran straight 30 weight oil.
I run, 10w-30 amsoil synthetic. It leaks a little bit of oil, but not to where I have to refill it every other day.

Just wanted some opinions on the weight of oil i should use, since it has to idle that like up to 1-3 hrs at a time depending. It doesnt over-heat, but I want to make sure its heavy enough oil. was thinking of putting in 20w-50 synthetic, and a heavier one I would assume would slow down the oil drips. I live in washington state, so the summers are kinda warm, winters are fairly cold, we're coming up on summer so just wanted to change the oil with the right viscosity.
Need the best for my money makin machine!
Thanks!
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I wouldn't call 2000 rpm idling. That is running at optimum just like going down a highway. It should be just fine on Amsoil 10w30. That would not be my choice though. Any 10w30 should be fine for it as long as it has good oil pressure.

 

15w-40 or strait 30

 

Lets first qualtify your truck, engine and useage. Your engine is still 1987 technology and the lubrication requirements are just that, 1987. Your engine is stuffed under the floor of a van. It is a hostile environment for any engine as it does not enjoy the free flow of air that an engine would enjoy under the hood of pickup. Prolonged light load running when running the PTO off of it can be murder on an engine especially noting the above conditions. Your truck and its useage is not normal conditions for any engine. Yours would be more inline with an industrial engine. Because of these factors, I would suggest using Amsoils 5w-30 Series 3000 Heavy Duty diesel oil. The numbers are:
VIS@100C 11.5
Viscosity Index 176
Pour point -60F
NOACK@ 250F less than 6%
HTHS 3.5 (2.8 is the bar for normal wear, higher is better)
TBN 12

You may want to start trending you engine via oil analysis. You should be able to easily get 7500 miles between changes. I would let the report be the deciding factor about that. Rarely, and I mean rarely, do I recommend Amsoil products to the general public. It's just is not cost effective. For you, yours is more an industrial piece of equipment and the additive package in the Amsoil would be of benefit to you.

 

If you still have the owners manual, read it carefully. Ford specifically recommends 200 hour oil change intervals for your type of service. Get an hourmeter (Hobbs) like on a stationary, aircraft or marine engine, they are not too expensive.

20W-50 is probably not a good idea, if the engine is not worn out and does not smoke. It will likely cost you money in extra gasoline. Straight 30 in summer and 10W-30 in winter is not a bad idea. Synthetic may not be good with bad seals, I would go back to dino.

Jim

 

The motor was rebuilt 5 years ago, so the seals should be in decent shape. The 200 hrs can be extended if used oil analysis shows the oil is good for it. Synthetic is probably a good idea given the heat. In fact, what about the tranny and heat? I run Mobil 1 ATF in my E350 motorhome auto tranny.

Hour meters are avail at JCWhitney, Harborfreighttool, and/or Northwesttool among others and can be had for around 25$. I almost got one for my pickup for fun.

 

I actually ordered one of those hourmeters from Northern Tool. It was not a Hobbs brand and it did not work with the Ford ignition system since it was designed for small engines like Briggs and Stratton. A Hobbs meter is usually connected to alternator output.

Jim

 

Staying with a xW-30 is fine, synthetic if the engine is sound. Going to heaver viscosities will load up the engine, i.e. increase the co-efficient of friction, which you don't want.

 

Flash states: "Prolonged Light Load Running..." FLASH, does this mean now that you are endorsing the use of Prolong engine oil treatment?! I thought you did not feel oil additives were necessary is a well maintained engine? Why, now are you changing your beliefs??! Why Flash?! LOL, Flash only kidding with you here. Just my warped sense of humor kicking in! :>) Ed