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I put 10w30 in my 73,000 mile 351 windsor because it gets quite warm here in Southern California. It is fall and by 9:00 am it is already 80+. Now below I attached a picture from my manual: Factory oil recommendations
Now above this it says “for engines 4.9, 5.0, and 7.5”. Why not 5.8? It seems dangerous not to put 10w30 in it during hot temps. Nonetheless it runs proper with this oil in. Is it possible it doesn’t refer the 5.8 because the 5.0 and it are the same?
The 5.8L has larger main (& rod?) bearings in it than a 5.0L, so the 5W-30 oil should be able to support the loads better in that engine than a 5.0L at the same oil pressure. A '95 5.8L also a roller lifter camshaft setup (compared to the 7.5L which is only flat tappet, maybe the 4.9L as well), so combined those might be the rationale for using the lighter oil in the 5.8L than the others. For what it's worth I've run 5W-30 in my 5.8L's for years without any bearing failures, from -35F to 100F.
The 5.8L has larger main (& rod?) bearings in it than a 5.0L, so the 5W-30 oil should be able to support the loads better in that engine than a 5.0L at the same oil pressure. A '95 5.8L also a roller lifter camshaft setup (compared to the 7.5L which is only flat tappet, maybe the 4.9L as well), so combined those might be the rationale for using the lighter oil in the 5.8L than the others. For what it's worth I've run 5W-30 in my 5.8L's for years without any bearing failures, from -35F to 100F.
So in your opinion do you think I should go back to 5w30? Or am I OK? I am undecided if I should go to full synthetic because I’m told it is ‘cleaner’.
edit: I’d like to add that even the manual says Synthetic is OK to use
10-18-2018, 01:01 PM
