10w-40
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Fleet Mechanic
Joined: Jul 2000
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From: SE Iowa
10w-40
Is there really any purpose left for 10W-40. Maybe its just me, but every new vehicle calls for 5W-30. All of us with older cars/trucks are using 10W-30 or 20W-50 depending on mileage. There just seems to always be an abundant supply of 10W-40 when I buy cases of 5W-30 and 20W-50. Just a thought.
Stryder
Stryder
Last edited by stryder; Jan 31, 2005 at 06:16 PM.
Post Fiend
Joined: Jan 2000
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From: Metro Detroit (Redford)
My F150 straight six likes 10w40. It is a great oil. Useful also to mix 50/50 with 10w30 to make an "in between" grade. No new car manufacturers are specifying it because 10w40 cannot meet the energy conserving tests and so it cost them on CAFE. To get the CAFE mileage, EPA strictly limits what they can recommend. Otherwise, they might say to use 10w40 in hot summer weather.
Posting Guru
Joined: Jun 1999
Posts: 1,642
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From: Northern California
On the other hand, why use a oil viscosity, that does not deliver maximum performance and benefit to an engine? To me, that's like running all four tires at 22 PSI as fuel mileage and tire wear suffer?...Today's modern SL dino oil, 5w30 and 10w30 are made to handle high heat conditions. Even towing. Not so 12-15+ years ago, but in a modern, tight, engine 10w40, 15w40 20w50, is not doing the engine any favors. Frankly, internal crankshaft pressure, is much harder. During cold starts, higher viscosity oil pumps slower, even in the summer. Over time, that causes unneeded engine wear, then one MUST use a higher viscosity oil, in a worn engine. Unless you drive a piston slapping beater (and we all own these types of cars and trucks) I would never use any oil thicker than 10w30. Not needed. Wasted money with lower MPG useage as well. 
Cargo Master
Joined: Dec 2004
Posts: 2,232
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From: NE Texas
For your old 300 I6, 10W40 could probably work okay except that in your climate you deal with pretty cold winters. Where 10W40 causes problems is in small highly stressed engines. In such applications the extreme quantity of VI additive necessary to span the 10 to 40 weight difference causes coking.
If you were in my climate where we deal with temps in excess of 100 degrees F for a few months of the year, 5W30 is not the ticket either.
Save the heavier weight oil for the Summer months and use the lighter stuff in the Winter.
Good luck,
Doc
ASE Master
If you were in my climate where we deal with temps in excess of 100 degrees F for a few months of the year, 5W30 is not the ticket either.
Save the heavier weight oil for the Summer months and use the lighter stuff in the Winter.
Good luck,
Doc
ASE Master
Post Fiend
Joined: Jan 2000
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From: Metro Detroit (Redford)
Originally Posted by MBDiagMan
For your old 300 I6, 10W40 could probably work okay except that in your climate you deal with pretty cold winters.
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There is nothing wrong with 10W40. Its practical operating range starts at 0*F just like the ever popular 10W30. I run 10W40 in the 350 I built last summer and in my ranger recently. I feel the added viscosity is beneficial to the 350 and I might as well use it in my ranger since I have it around.
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For gas motors I sure like some of these 5w-40's out there vs some 10w-40's . They generally cost more though .
5w-40 Valvoline would be a good oil for the 300 , 302 , 460 ect . Probably except the far north it could be an all season oil .
That Valvoline Premium Blue Extreme 5w-40 would make a good warmest 6 months of the year oil in quite a few engines . So would Citgo Syndurance 5w-40 syn blend @ only 2.99 per quart
I believe every oil maker has one or two standouts in their line-ups these days .
5w-40 Valvoline would be a good oil for the 300 , 302 , 460 ect . Probably except the far north it could be an all season oil .
That Valvoline Premium Blue Extreme 5w-40 would make a good warmest 6 months of the year oil in quite a few engines . So would Citgo Syndurance 5w-40 syn blend @ only 2.99 per quart
I believe every oil maker has one or two standouts in their line-ups these days .
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