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I have a 2008 Bullitt with 4.10 gears. My gear oil is motorcraft 80w90 with the frict mod added would I be better with the Royal Purple 140. I only have 3000 on the oil. Please advise. Thanks And how often should it be changed.
 

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Bob The Mo'fukkin Builda!
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if you want to pay for the fluid sure, but you'll be fine waiting till it needs to be changed. did you just get the 4.10's installed. if so you may want to change it after about 500 miles
 

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Royal Purple doesn't need additional friction modifier added to it. It already has additive in it for LS.
 

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With 4.10's I would think you should use the 75-140W.

I just picked up some Mobile 1 for my gear change. Ford say's to use synthethic.
 

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Ok, this is going to sound stupid, but, after talking to a few people that suggested Royal Purple motor oil, I tried it.. And It felt like the car made more power.. I thought I was nuts.. So then my GF wanted to change it in her jeep, and she wanted RP, after the oil change the jeep has more power, no doubt, before in 6th gear you couldn't pass, couldn't do anything.. just sit where it was, didn't matter how hard you stood on it.. now it has power to pass..

This is so retarted because when I used to work for the race team, over the years we ran all sorts of different oil, Kendall, Amsoil, Schafers, and Brad Penn.. And oil is oil.. if a certain brand made more power, we would have been on it.. The engine builders spend hundred of hours on the dynos, trying to squeze every last horse out of these motors.. Only oil that I have ever seen different was the Schafers, it was sticky.. if you got it on the car, you couldn't get it off!!!

So like I said, this makes no sense to me.. but its the truth.....
 

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Bob The Mo'fukkin Builda!
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you aren't the first person to notice this.

only reason i don't use rp in everything is because of the cost. i use mobil 1 for everything except the 07.
 

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There's no doubt a lower viscosity oil will reduce parasitic losses. I know a guy who swears they pick up 1/2 tenth by using 75/90 instead of 75/140 AND not filling it all the way. Well know fact windage trays and keeping the oil off the crank improves HP.

I'm a little skeptical that you can "feel" such a big difference, but hey, whatever works for you.
 

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There's no doubt a lower viscosity oil will reduce parasitic losses. I know a guy who swears they pick up 1/2 tenth by using 75/90 instead of 75/140 AND not filling it all the way. Well know fact windage trays and keeping the oil off the crank improves HP.

I'm a little skeptical that you can "feel" such a big difference, but hey, whatever works for you.
I know!!!!!!! thats what I said, no way I can feel it.. but in the jeep, absolutly!!!! Strange.... And you are right about keeping the oil off the crank, thats why guys run dry sumps with huge balloned out oil pans..

All I can say about RP is werid.. and spendy.. when I open up the motor next week Ill be able to see how the oil looks..
 

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I used red line oil and its quite as a mouse.
 
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