[Tokay444]

Originally Posted by KillerBMotorsport

On a stock engine, this is a bad idea. Will your oil pressure go up, heck yes! But your oil flow will absolutely go down. To run heavy weight oil, the engine needs to be properly built for it. There is a stark difference in the flow dynamics of 0w-20 vs 10w-50. Hot temp characteristics are going to be poor, but the base going from 0-to-10 is worse.

The right thing to do here is send your oil out for analysis. Know what is going on with internal wear, then bump the viscosity up one step, then check again. Don't be surprised if the best results are obtained by the factory recommendation. Many, many times we hear of tech giving outlandish recommendations all the time with no clue, and definitely no thought to actually testing results from the recommendations they give. Tread lightly!

The only time I would consider swapping oils is if you're observing severe temperature swings between your daily driving and track time. The right thing to do there, is use the best oil for each job. Change the oil before a track day and bump a step up (not double). Based on temperature/flow profiles a decent bump in normal temperature (say +25-50 degrees f) with a one-step higher grade of oil, will give you very similar flow rates to the thinner spec during daily driving temps.

Ideally, you right the proper oil for the conditions your car will see 90% of the time.

Standard Mustang GT 5W-20. Track pack? 5W-50. Exact same engine.