transmission fluid check eaton fuller

Synthetic 50 weight is what my 2000 had in it from the factory.

 

huh, maybe I should go with synthetic.

 

what transmission oil do you recommend I put in as far as longest to last and most reliable? I run TX to PA and back, 2-3 trips a week. I figure synthetic would be better than conventional (prices aside). Should i get 50w or 75w-90. TA quoted me for 75w-90 but I heard people recommend 50w. Which one's better? I have a 1999 freightliner with 13 speed eaton. Thank you so much

 

If just general freight hauling, I'd do 50w for the ever so slight mpg improvement.

 

is that 50w synthetic? Thanks

 

Doesn't matter.

 

It isn't critical, though I personally would use synthetic unless you plan on selling the truck in the next year or two.

 

i think im gonna transfer my BS falling apart truck to all synthetic. It seems that high end synthetic oils like amsoil show overwhelming benefits compared to conventional. Thanks

 

You have a 99 fld120.... If it hasn't been full of synthetic before now you're wasting dollars..... rebuild it first then change to the good stuff

 

If your truck is falling apart, you've got more important places to spend money than lubricants.

That said, synthetic fluids offer small, but real, benefits. See page 14: http://cumminsengines.com/uploads/docs/cummins_secrets_of_better_fuel_economy.pdf