5-40 synthetic oil? - Ford Powerstroke Diesel Forum
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post #1 of 4 Old 04-05-2008, 05:37 AM Thread Starter
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Cool 5-40 synthetic oil?

Hi Everyone. First, thanks to all of you contributing on this forum. I have learned a huge amount about my ps. I have a 97 f-350 crew cab, 7.3ps. The truck has had alot of new parts, like new injectors, rings sets, glow plugs, relay and so forth.
My question; CAN I RUN ROTELLA T 5-40 SYNTHETIC OIL IN MY POWERSTROKE? My truck runs exceptionally well once warmed up, but runs very very rough when 1st started up, even if temp in the 70's. That is if it sat and cooled down, say after being parked for 8 hrs, when ready to leave work. All the glow plugs and relays test good. I just think it is the thickness of the oil, and the fact my truck has 356,000 mi on it. once warmed up runs like a champ. Thanks for any help.
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post #2 of 4 Old 04-05-2008, 05:51 AM
Stupidity pisses me off

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I'm running amsoil 5-40
Are you in cold climate?


99.5 F350 Super Cab Long Bed, Dually.

Originally Posted by SMKSTAX View Post
You are not right man, but i still think your funny as hell!
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post #3 of 4 Old 04-05-2008, 06:00 AM
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I changed out to Rotella 5w-40 Synthetic before this winter and it was night and day on the starting. I don't have the opportunity to plug it in during the winter so it always start cold. I have no trouble all the way down to zero with the syn. Idles much smoother as well, no "romp, romp" when cranking and cranks much faster. There is not problem running syn in your engine or switching back if you want, many many people will tell you this and if anyone tells you not to run syn because it will mess something up or not to switch back than the don't know what they are talking about. I had my Air intake heater (which you're probably doesn't have) and all my GPs and GPR checked out too. Alot of people also run 5w-40 all year round.

Although rough starts in 70 degrees shouldn't really be happening, are you seeing excessive white/black smoke when starting at 70 or below?

2003 F-350 7.3 SC
Isspro Gauges
MBRP Exhaust 4in
AFE Stage II
33in Toyo MTs
DP Tuned Stock, HI, 40t, 60t, 80t, 80e, 120r, 140ex
6.0 Trans Cooler
08 Tow Mirrors

Too much mud
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post #4 of 4 Old 04-05-2008, 03:02 PM
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i run Amsoil 5w-40 in my 2006...luv it !!!
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