Delvac Or Rotella Oil

Sometimes - depends on how exactly the engine is consuming oil and the rate of oil consumption. Delvac and Rotella are considered diesel motor oils - as such, have a very robust additive package and setup for the harsh environment that is norm on a diesel engine. They also tend to run on the viscous side - generally won't see these running under 10w30 or 15w40, especially in most US states.

The caveat is that this additive package - when used on a gasoline-fuel car that consumes oil - can potentially kill your catalytic converter very quickly. The additive package that protects a diesel engine, was never designed for a gasoline engine and will eventually poison the cat.

Doesn't work the same on every case - some people can run Delvac and Rotella for years, helps oil consumption and extend motor life - others run it and end up with a dead catalytic in a couple of months and worsening oil consumption.

Not particularly hard to find these oils - usually setup in a separate section of an autoparts store, usually by the motorcycle fluids section. Reason why is they don't want you to accidentally use this in an improper situation.

Myself - I've used Rotella in some special cases - like in pre-1974 car that was intended to run on leaded gas, before catalytic converters were put on cars. Those case, the oil is awesome - good additive package, lots of high pressure additives to help with metal on metal contact.

On a modern gasoline engine - depends on what the situation is. If oil consumption was just starting - I'd look into other possible fluids to use. In cases of exceptionally heavy oil consumption - where the original cat might already be gone - worth a shot to run, just to see if it does anything - at that point, it is more last ditch fix sort of thing.

The common case where oil has gelled or plugged the oil return holes (stuck rings) - actually shown that "thinner" oils help break through and help oil flow past there.

Correct - look at the viscosity of the oil and their kinematic viscosity (data sheet) + some oils are known to shear down in viscosity, like Mobil 1 oils.

You can also look up PDS (Product Data Sheets) on most manufacturer websites - look at the viscosities of the oil - some tend to be on the "thin" side, others on the "thick" side.

Example a 20-weight oil (0w-20,5w-20) here it generally lists cTs @40C and 100C, a 20-weight oil can range from 5.6 to 9.29 cTs @100C. Most oils sit in the middle of that range, but some can be a hair on the "thin" side - closer to 5.6, others sit higher - closer to 9.29.

But in the cases of Delvac and Rotella - it is more than just viscosity, it is also additive package chemistry. The additives were designed for the harsh environment of diesel engines, that gasoline engines don't see. Gas engines run cooler, usually see more frequent oil changes, and don't see the contaminants that diesel engines see.

But like all things, manufacturers don't make anything ease. As there are now "mix-fleet" diesel motor oils. Good example is Rotella T6 synthetic. You can also tell if they are mixed fleet as they will list the C-designations for diesel engines as well as the gasoline engine API startburst ratings. What this means is that the additive package has been modified to be more universal in application. But IMO, this makes diesel oils less attractive than what they used to be - as that robust additive package and dispersive ability is what made it popular in the first place.

That's why I recommend not to use these oils unless you know what you are getting into. This is not an automatic fix for cases of oil consumption - indeed in some cases, it could cause more damage than not. Bottom line - don't count on miracle oils or different oils to "fix" oil consumption. You have to find out the exact cause, then do what needs to be done to fix it right the firsts time.