It may also be true that breaking in a SHO engine with synthetic oil any create problems problems with ring seating. Many expensive cars come filed from the factory with Mobil 1, but they were designed for break-in in with Mobil 1. I have used Mobil 1 since my first oil change at 500 miles and may try conventional oil this summer in an effort to pick up a few HP.
Without expressing a preference for synthetic or conventional oil, these general rules maybe help full.
You may do your own web search on oil additives and treatments.
Ford Motor company does not recommend them.
The Justice Department has prosecuted most of them for fraudulent claims.
API does not recommend them.
Any year SHO has a well designed reliable oiling system, it has to because it has a very difficult job. Every year SHO pumps 7 GPM at red line or pumps a quart every 2 seconds. Bearing clearances are VERY tight This is engine that thrives on oil volume not excessive oil pressure.
If you try Prolong, STP, Slick 50 or any other oil additive you can lose and engine the SAME DAY. I could be wrong, do let them test it on a SHO engine, get it writing. Fact is, no reputable authority recommends and no body reputable makes it.
I hope this helps, if you are still not additive shy, read below:
OK! I know I should have started reading about Slick 50 a lot sooner, but, I didn't. I had my oil changed 12/16, Iíve used synthetic for about 9 months with no problem. Jiffy Lube recommended Slick 50 engine cleaner because it had been 5000 since my last change. The engine ceased that evening. Dealer says it will cost over $10K to have it rebuilt. Jiffy Lube wants a complete diagnosis after the engine is taken apart. I need an SHO engine authority recommendation. Two valves are dead - no compression, and my heart is broken. I am impeccable about the maintenance of this car, Ford doesn't care because it's out of warranty. The dealership has never seen an SHO engine go. I may not know all there is to know about this car but I've owned and driven a lot of cars and there is nothing out there that hums like "After Midnight".
Iva L. Hairston