I couldn't tell any mpg loss with the 85w140 but I didn't really care or check too closely. The vis. index jump from 75w140 to 85w140 is almost as big as the jump from 75w90 to 75w140. The 85w140 is great for hot weather and working hard. I've used Valvoline semisyn 80w140 with good luck. Craig

 

I've used 75W-90 up front and 75W-140 in the rear the last couple of oil changes, but next time I'm thinking of going to 75/140 in both so I don't have to have (2) half-quart jugs of oil left over. And save a few bucks in the process.

A fuel mileage hit for the heavier stuff? I guess it makes sense but I've never noticed anything.

 

I think the mileage as said does makes sense but I think it would be so minor that you wouldnt even tell. Maybe if you drove the same way everyday, same MPH, same weather, same traffic, and same hills you THEN might notice

I need to order my PML rear Diff cover so I can get that on and some new fluid in anyone know the best place to get the cover?

 

probably the best place to get the cover is directly from PML at www.yourcovers.com.

Anyone with experience on the new Amsoil 75W-110?

 

Genos is a little cheaper
.http://www.genosgarage.com/products.asp?dept=167

 

If I remember my auto mechanics course from many many moons ago correctly, in a multi-weight oil, the minimum viscosity of the oil is the lower number. The oil increases in viscosity towards the higher number as the temperature of the oil increases, the maximum protective viscosity being the higher number. This applies to any multi-weight oil. 10w40, 20w-50, 75w90, 75w140 , etc. A little research on the NET would verify if what I have recalled is correct.

 

About 30 yrs ago a lube salesman told me the lower # is the vis at 0C and the higher # is the vis at 100C. He also said in his early days of sales (before multi-vis) racers made their own oil mixtures and refrigeration oil was one of the ingredients. Years later I read that even tho multi-vis lubes seem to get thinner with heat the lube properties actually go up. Craig

 

thanks. Does Genos have the powder coated cover?

Here's a link for the Amsoil 75W-110. Just introduced at the end of January.

http://www.amsoil.com/AmsoilLogin/De...spx?zo=1132530

 

Im not sure too many people will actually recommend the powder coated once since its actually an insulter so it almost defeats the purpose of getting an aluminum one. Atleast another website that I found it on states this...

Quoite from DPPI...You might also notice that the covers are NOT powder coated! You are buying a high capacity cover to lower fluid temps and prolong the life of your differential, powder coating is an excellent insulater, it holds the heat in the cover!
Heres there website also same price as Geno's http://www.dieselperformanceparts.com/products.cfm

 

That's why I got the "raw" PML covers.... more functional, less expensive, and I preferred the way they look.

 

I've read that as well, don't know that I fully agree because the Mag-Hytec cover is powdercoated as well. Primary reason I want the powdercoating though is for longevity, unless the raw cover is clear coated, I'd prefer to have it powdercoated so its got some protection from the environment.

I'm open to suggestions though, saving $60 on the cover would buy a few fuel/oil filters!

 

How much weight on the rear axle is considered significant enough to switch to 75w-140 over 90?

 

It's not about the weight the truck is carrying, it's about the operating conditions. Such as towing in high heat or light duty use in Alaska. Things like that. The load and temps the gears are seeing.

Mine began to chatter a bit at about 110,000 miles when I was pulling hard from a stop. So I switched to 75-140 Mobil 1 and fixed it.

John

 

i use this...

Red Line ShockProofTM Gear Oil
A unique lubricant containing a suspension of solid microscopic particles as an extreme pressure agent. The viscosity characteristic allows the lubricant to resist throw off and provide a film thickness that can be rated as a 75W140 gear oil, yet has the lower internal fluid friction of a 30Wt motor oil. Popular uses; gearboxes and transaxles designed for racing, Formula Ford, Sports 2000. Recommended for heavily loaded racing differentials and transmissions which see shock-loading. ShockProof contains a unique solid dispersion which cushions gear teeth to help prevent tooth breakage and allows the use of lower viscosities. Available as SuperLight, LightWeight, and Heavy grades

the heavy is roghly a 75w-250