Have you ever run diesel oil in your engine?

[RebekahsZ]

Perfect timing on this thread. My truck (the one I tow the Z with) has had normal 40psi oil pressure on the guage at cold temps, but when towing and good and hot, the oil pressure reading on the guage drops to 20 at cruising rpm 2000-3000rpm. Noticed it returning from the track this Saturday night. Once motor cooled, oil pressure was back at 40. 1) should I be worried? 2) should I try a different oil? It currently runs 5W30. I'd like this motor to last at least a few more years so I can concentrate on the Z-car. I know hybridz isn't automotive 101, but I trust you folks best.

[randy 77zt]

Rebekah-I would test your oil pressure with a good mechanical gauge before doing anything else to the truck.you can get very good pressure gauges cheap at your local bearing/industrial supply house-you get that plastic air shock line and some fittings and run it in the cab.If the truck has some miles on it I wouldnt run that 5w-30 stuff.I would run at least 10w-30 in the winter and 10w-40 in the summer.Or 15-40 diesel oil like delo or rotella.Usually low oil pressure is the sign of worn rod or main bearings.Do not worry-put better oil in it and run it till it blows.Alot of goverment fleets run delo or rotella in all thier vehicles-they dont want to stock different oil for different apps-this makes for confusion.In a multi-viscosity oil like a 5-30 the base oil is 5w-an additive package is added to it that seems to be a type of plastic resin that changes viscosity with heat.But too much heat-or a wrong application like motorcycle engines-shears up the additive package and you are left with watery 5w nasty stuff.I did this to a motorcycle engine in baja.Diesel engines and motorcycle engines usually use the motor oil to lube gears-either cam drives or transmissions-standard car oil gets the additive package shredded when used in gears.Alot of race engine builders havent gone for synthetic oil yet-they seem to prefer a high quality standard oil like Brad Penn .http://www.penngrade1.com/Default.aspx