Engine 88 got oil question

Comp Cam

Member
Jan 11, 2019
41
2
8
21
Lenexa,kansas
What's up, so it's time to change the oil in my GT. It's HCI bigger throttle body rockers and Pushrods with gt40 heads. For some odd reason he used 20w 50 racing oil in it for a recent oil change (before I bought it). Unless he's trying to hide unwanted noise (witch I fear). Should I go ahead and use 10w 30 or stick with w20 50 instead?
 
  • Sponsors (?)


John Dirks Jr

5 Year Member
Jun 28, 2013
2,199
872
174
55
Maryland
Some engines are built with slightly more bearing clearance for racing purposes. I dont have a technical explanation for why. The 306 in my 93 vert was built that way by a previous owner. If I run 10-30 in that motor, hot idle pressure drops too low for my liking. So I run 20-50 Mobil1 full synthetic and its perfect. My 92 was built with factory spec bearing tolerance and I run 10-30 in it.
 

Wayne Waldrep

Active Member
Apr 14, 2003
239
142
53
52
Cuba, AL
My original engine went 248k miles. All it ever had in it was Castrol 20w-50 conventional. Like has been said above, either is fine.
 

Mustang5L5

Mod Dude
Feb 18, 2001
30,312
6,903
224
Massachusetts
Can you put a good oil pressure gauge on the car and see what you have for pressure now, and then see what you have if you change to 10W-30? That will likely give you the answer you need once you see how the different oil affects pressure (either cold or hot)
 

mikestang63

SN Certified Technician
Aug 27, 2012
9,796
6,566
204
In the garage
as long as you dont live in a cold climate, you can run it fine. Just to throw you a curve ball, I've been running Rotella 15w40 in my N/A fox body cars for decades and 20w50 castrol in my supercharged ones.