I've been wanting to ask this for a long time (75W-140)

[SMILEY]

Thanks for the info Grossomotto. It looks like it will work quite well. I dont do any towing but do haul heavy loads on occasion. Im sure even a bit of towing now and then would be fine as well.

 

[Grossomotto]

quote:

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Anyone know the viscosity difference at operating temps? I am hoping to save some MPG.

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From the RedLine site (http://www.redlineoil.com/pdf/5.pdf)

RedLine 75W90
visc@100ºC,cSt 16.4
visc@40ºC,cSt 115
pourpointºC -45
flashpointºC 440

RedLine 75W140
visc@100ºC,cSt 27.4
visc@40ºC,cSt 180
pourpointºC -45
flashpointºC 440

You can see how much thicker the 75W140 is. I would think your gas mileage will be slightly better with 75W90 and protect just as good. Unless you're towing a trailer, RedLine 75W90 is just fine.

 

[Grossomotto]

Just for the record, I run RedLine 75W90 in my Toyota FFdiff/RRdiff/Tcase and MTL in the manual trans. I love the stuff.

 

[brianl703]

quote:

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Originally posted by MolaKule:
For the most part, Ford uses the 75W140 as their "lifetime" fill for differentials. It's a so-called hedge against differential failures until the drive train warranty has expired.

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The factory fill for my 88 Mustang 5.0 is 80W90. The recommended change interval is every 100,000 miles.

What's the Ford recommended change interval for differentials filled with 75W140?