95 Mustang GT engine knock

[95 GT]

I have a stock 95 Mustang GT 5.0 engine that I bought new. Every summer in Arizona when temp. excedes 100 I get a really bad engine knock.
Tried to increase octane with 89 and 91, car only has 43,000 miles on it
and it runs perfect in the winter. Any help would be appreciated.

[MonteCitan]

try running thicker oil

in the summertime I had to run 20w50 in my '89 to keep perfect oil pressure, it'd hold its own with 10w30...

but at least its worth trying a heavier weight oil

[Tbird232ci]

I think he might get some detonation.

[95 GT]

Tried 20-50 and found no difference.

[Zim]

Have you advanced your timing at all? Try running 93 if its in your area, thats weird though..

[MonteCitan]

can you hear it if you rev it up a bit under the hood?

[95 GT]

No problem when I rev it under the hood,only when car is running at it's hottest temp. and there is a strain on the engine while driving.

[Zim]

Sure its not an exhaust leak?