Been using Royal Purple HMX 5w-30 in a Toyota 3.4 V6 and a Chevy 5.7 LS1. Both have just over 130k miles. The 3.4 doesn't leak any oil, but the LS1 only seeps from the timing cover. Both engines are extremely clean with almost no varnish on the heads, and don't consume oil.
Will both these engines end up leaking from every other seal if I switch to a normal Synthetic 5w-40? I know high mileage oil has seal swellers, and my engines are over 15 years old. I'd really like to get them off the high mileage deal, but if need be, do I have to stick with HM forever? Tell me your experience if you ever got an oil leak switching from an HM oil.
From what I researched, these engines use thicker oils overseas than the US, and 5w-40 add-packs are more potent, kinda like high mileage oil. I drive my vehicles briskly here in Tucson where temps can go over 110. I've seen oil temps rise above 220 lol, so 5w-40 is sounding pretty good.
Will both these engines end up leaking from every other seal if I switch to a normal Synthetic 5w-40? I know high mileage oil has seal swellers, and my engines are over 15 years old. I'd really like to get them off the high mileage deal, but if need be, do I have to stick with HM forever? Tell me your experience if you ever got an oil leak switching from an HM oil.
From what I researched, these engines use thicker oils overseas than the US, and 5w-40 add-packs are more potent, kinda like high mileage oil. I drive my vehicles briskly here in Tucson where temps can go over 110. I've seen oil temps rise above 220 lol, so 5w-40 is sounding pretty good.