Q.
Your Auto question and answer advice about a person that has a Dodge Cummins engine leaves me a bit puzzled. He said that the temperature sometimes reaches minus 30C. Why would he want to heat the oil? First, if he is at that temperature should you advise him to use 5W-30 oil? Secondly, does he not understand what multi-grade oil is?
At minus 30, the 10W-30 oil is at its thinnest and easiest to flow. If he applies heat to the pan, then the oil will be at 30W and very thick. The engine will be hard to hard to start and accept a thick oil to a cold engine. What do you think?
George
A.
First, the recommended oil viscosity for a Dodge Cummins diesel engine is 15W-40. Using a lower viscosity oil such as 5W-30 would enable the engine to crank over easier in cold temperatures but wouldn’t necessarily provide the best protection for engine parts due to the high loads placed on diesel engine bearings, pistons and crankshafts.
Multi-grade oils such as 15W-40, 0W-20 and 5W-30 all have different viscosity (the ability to flow), with the lower the number the easier the oil will flow. Heating any of these oils by using an engine oil pan heater will enable the oil to flow even easier during cold starts so all engine parts will receive lubrication faster during initial engine start, but heating the oil will not cause it to “thicken” to the higher viscosity rating of the oil.
Modern multi-grade oil viscosity numbers only represent the viscosity of the oil and provide a description of the characteristics of the modern oil chemistry. In 5W-30 oil, the 5W describes the ability of the oil to flow in cold engine start conditions. The 30 describes how the oil film will protect engine parts in high heat conditions. The viscosity of the oil remains fairly stable under both cold and hot conditions to protect the engine under all driving conditions.
Modern engines are designed to use specific types of oil. Many current vehicles use 0W-20 oil but there are now a couple on the market that use the latest 0W-16 grade oil. For most older gasoline vehicles though, 5W-30 oil will work fine, with diesel engines running 15W-40 in all but arctic winter conditions.
Q.
I would like some advice concerning my 2012 GMC Sierra truck. For a number of years I have noticed a problem with low oil pressure on the gauge. The truck has approximately 160,000 km on it and doesn't burn oil. I have brought it to the dealer where I bought it a number of times even when it was still under warranty, and they say the problem was fixed each time.
I have been told my engine is worn out, they don't build them to last much more then the aforementioned mileage, that the recommended synthetic oil breaks down over time, though I go for regular oil changes, that the sensors aren't reliable, and that the gauge is just a guide. I am my wits end on how to proceed.
Do I bring it to an independent shop for an opinion or do I continue going to the dealership? Any advice would be appreciated, thanks.
Bob
A.
Normally I recommend staying with a dealership or reputable repair shop rather than going to different shops, but in your case you have given the dealership several opportunities to look at the problem without easing your concerns. Therefore I would recommend you go to a different repair shop.
Modern engines will typically go at least 300,000 km with routine maintenance (although there are always a few that fail much earlier). Also synthetic oil doesn’t break down like conventional oils, but does need changing on a regular basis just like conventional oils. Carbon, acids and other contaminants are trapped in the engine oil and that is why we need to change the oil regularly.
You should have the repair shop install a mechanical oil pressure gauge and check oil pressure with the engine at full operating temperature. Factory gauges are often inaccurate but as long as they read consistently, they are good monitors of engine oil pressure. If the engine bearings are worn, oil pressure will be low at all rpm but I suspect your problem is just low factory gauge readings.
