What oil to run-synthetic or convrntional

[wyominggun]

Just bought my first Grand national. I need to know what weight oil to use and synthetic or conventional, also if I should use a additive like lucas. Here are the engine details below. All engine machining and assembly along with head work was done by Gromms Performance in San Jose Ca

Factory LC2 block, with billet main caps, JE pistons, ARP bolts throughout, deburred and reliefed stock rods, crane roller cam, copper gaskets, and king bearings, remote oil filter with double capacity and braided lines.

Champion iron CNC ported heads with larger intake/ exhaust valves, 1.65 ratio rockers with hardened shafts, RJC valve cover spacers and "Buick Motorsport" black valve covers with K&N breathers

Ported factory intake, Accufab 70mm polished throttle body, Hemco polished doghouse, Precision PT52 turbo, ported factory headers( welded to prevent cracks), Precision front mount intercooler, 55lb siemens injectors, 2 Walboro 340 fuel pumps on an ATR hanger, modded ECU for low impedence injectors, new coil pack, underdrive pulleys, adjustable fuel pressure regulator with pressure guage, Nick Mchale heavy duty 3 row radiator, ATR 2.5 inch stainless exhaust, Terry Houston 3" down pipe with ATR wastegate

PLease advise what I should use. Car will be used for "sunday driving". No drag racing but will get on her once in awhile. I live in Western NY area so never really hot, car will only be driven during summer months and stroed the rest of the year. Thanks ahead of time for your help

 

[Boost231]

valvoline racing oil 20-50 with a 1/2 bottle of EOS

 

[sailbrd]

Amsoil 15-40 marine and diesel oil. Getting to hard to get EOS.

 

[wyominggun]

Thanks guys, keep the suggestions coming. Not sure why the previous owner stated that the engine was built to use conventional. I am thinking about the Rottela t oil.

 

[BlackBandit]

I would run the lightest oil you can while maintaining your desired oil pressure. If you get the pressure you want with 5w-20 then run it. You'll get better volume that way. FWIW the first number in a multi weight oil can be thought of as what weight oil the oil behaves like when cold. The second number is what weight oil it behaves like when warm. If you have the option of running a 0w-30 or a 10w-30 then you should go with the 0w-30 because (and this is important) THEY BOTH HAVE THE SAME VISCOSITY WHEN AT OPERATING TEMPERATURE!!! The only difference is that when cold the 0w-30 flows like a 0w oil and so will provide better initial protection. Also, if a 20w50 gives you 65psi warm with some rpms and you get 60 psi of pressure warm with the same rpm and a 0w-30 you should probably run the lighter oil. The reason again is the additional flow you would get which equates to better bearing cooling. One last thing. Idle oil pressure is necessary but is not as important as people think because the engine isn't under load. HTH. james

 

[Underboost]

I run Royal Purple

XPR 10W40 is designed for marine, oval track and endurance car racing. Capable of withstanding long intervals of extreme heat, it works especially well with alcohol and methanol. It is extremely popular in sprint cars, late models and World of Outlaws racing.