10W30 in 98 F150 w/ 5.4

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May 18, 2003
I have a 98 F150 w/ the 5.4l. It was purchased new and switched to M15W30 at 1000 miles. I have always run the 820S filters. Oil changes have always been around 5000 miles, but over the last 20k around 10k. The truck has always burned about 1qt over 5000 miles. It currently has 75K on it.

After reading through this board, I changed the oil and put in 10W30 M1. I bought a 5qt jug from Walmart and added 1qt of M15W30, which I had leftover.

I want to verify that the mixture of the two weights will be OK.

Does anyone think the truck will burn less oil with the heavier weight? I live in TX, so this summer will show 100+ degree days.

How about running 10K changes? The oil was very "thin" coming out, but it was also very hot after a 25 mile run... I will test the oil after the next change, but that will be 4 months or so from now...

Originally posted by jscott:
added 1qt of M15W30,

Do you mean 15W-50??

Anyway-yes you can mix the two. I do it in my Toyota Truck which uses less when I mix.

I would not go 10K miles without an analysis. I would play safe and limit it to 8K for the first time.
I think he meant M1 5w30 - just no space betwen the M1 and 5w30.

As far as mixing the 5w30 and 10w30 M1's - there should be no issues there.

Will you burn less oil? Maybe. Reality is the 5w30 and 10w30 M1's are both relatively thin oils, though they don't seem to shear back very easily these days (which is a good thing!). With that in mind, consumption may or may not decrease since the two are relatively similar.

While M1 is good stuff, I wouldn't feel comfortable going to a 10k change without analysis. Regular interval on these engines is 5,000 miles, which is where I would at least check the oil first.

Good luck!

[ May 23, 2003, 10:54 AM: Message edited by: MNgopher ]
Both oils are 30 weights. I doubt that you'll see any difference in consumption. Try a 10w-40 if it concerns you, but note that 1 quart over 5000 miles is not significant. Even 1 quart in 3000 miles is normal for many engines.

Originally posted by MNgopher:
I think he meant M1 5w30 - just no space betwen the M1 and 5w30.


I agree with you
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