Originally Posted By: fsdork
Originally Posted By: AdRock
I have an '02 GT also, I run a 5w30. The spec for it is 5w20 but Ford only did that for CAFE. These 4.6's were originally spec'd 5w30.
Can you cite an application where the 4.6 2v was spec'd for 5w30? Also, if there is any credible information indicating there were no revisions to the engine which would necessitate the change to 5w20, I would be interested in that as well.
Here's a post from Corral.net that explains things and has quotes from Ford employees.
Quote:
Many people have provided valuable information on the proper weight oil to run in our modular engines so I thought I'd condense it into a single post.
The bottom line is, we really shouldn’t be running 5w20. The switch from 5w30 in 1999 to 5w20 in 2001 (on identical engines) had nothing to do with wear or reliability issues and everything to do with Ford saving a few bucks by meeting CAFE standards. At the time Ford was fined $5.50 for every 1/10th of a MPG under the target average of 27.5 MPG for every vehicle manufactured. To help meet the target Ford changed from 5w30 to 5w20 and was able to improve mileage by 1/16th of a MPG and meet their goals.
Here is a quote from one of Fords Product Design Engineers:
Mike Riley, Product Design Engineer with Ford Motor Company:
Quote:
"Moving to 5w20 was driven by ... CAFE requirements. The company believes the switch to lighter viscosity 5w20 oils will reduce carbon dioxide emissions by 190,000 metric tons a year and reduce US fuel consumption by over 21,000,000 gallons a year."
While most people understand the main function of oil is to protect the engine, Ford's only concern in that respect is that the engine survives the warranty period. I especially appreciate Scott Whiteheads insight on this topic. He worked for Ford testing different oils in modular engines and here is what he had to say:
Scott Whitehead - Engine Development Systems Engineer, Ford Motor Company:
Quote:
"I've seen the dyno testing. I've probably looked at several hundred engines disassembled and spread out on inspection tables. And I've been involved in testing to resolve issues where varying the oil viscosity was part of the test. Please do not put 5w-20 or less into a mod motor. Please. This is especially true in 4v motors. 5W-30 is probably a good oil for the street with mixed temperatures."
Ford Racing Group apparently feels the same way:
FRPP Group:
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"DO NOT go back to using 5w-20"
Real world experience seems to back up the advice of these experts too. Some of the best data from the modular community has come from Nick McKinney:
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"I have said it a few times now, heavier oil has better protection especially in the cam bores. ---I get 2-3 sets of modular heads a week through here, and any lay person just from looking would pick the 500,000 mile cores run on 15W-40 diesel spec all their lives over the typical Mustang head run 50,000 miles on the light stuff"
Fleets typically run their vehicles 250,000 to 500,000 miles! I've heard Nicks experience echoed several times by fleet managers. They wouldn’t run a 5w-20 oil for one minute.
There have been concerns over bearing tolerances and lash adjuster pump up with heavier weight oils but these are largely overblown. Bearings tolerances haven’t changed since the 60's and much of the small difference found at the crank bearings is because of the aluminum blocks different expansion rate. A reality check for those concerned is the fact that while the 01+ modulars were spec'd to 5w-20 oil, the exact same engine pre 01 was spec'd with 5W-30. When Shelby modifies the 4.6's he covers the 5w-20 spec sticker under the hood with a 5w-30 spec sticker. In Australia all their modulars are spec'd for 5w-30 and higher because they have no CAFE standards. And the GT500/GT's with the exact same bearing clearances are spec'd for 5w-50w oil.