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You'll find this viscosity oil speced in almost all of the factory performance cars and in cars like the Roush. You'll also find the oil delivery system is different than that of the same engine but in a normal vehicle. The reason for the viscosity spread is simple. The 5w gives the engine a faster oil pressure build at cold startup and it ensures lubrication a hair quicker. The thick end of the oil is for fuel dilution which is expected with any high performance engine. It's common for fuel to make up 5% of the total weight of the oil in the pan for a performance engine. That's the result of hard running and lots of fuel going thru the injectors. Some of which ends up on the cylinder walls and is washed into the oil.
You have it backwards. A 5w oil will lubricate quicker than a 15W oil, but the thicker oil will build pressure faster, as it's harder for the oil pump to push through the engine. Thinner oil gives lower pressure readings.
You have it backwards. A 5w oil will lubricate quicker than a 15W oil
Sorry, but you're making a common mistake. Oil pressure is not built until the fluid reaches the farthermost point in the lubrication system. The 5w will get there far faster than a 15w. Where you're making your mistake is if you take a mechanical gauge and put it on most car engines, the 15w will show pressure quicker than a 5w. The reason is most engines have the oil sender port right at the oil filter which is the very start of the lubrication system. What you are reading is not oil pressure but the fluids resistance to flow. Take a Powerstroke, as an example, the oil pressure sender is on the very end of the lubrication system. It may be several seconds before it reads any pressure at all. Using a 5w-40 cuts this time by a lot. Where you might see on a mechanical gauge 70lbs of oil pressure at the filter, on an engine with the oil port at the end of the lube system, you might only see 15lbs at 2000 rpms and lower at idle, sometimes as low as 5lbs. There are major advantages to having the sensor port at the end of the lube system. The biggest is that you'll know when the engine is worn and needs a basic overhaul before serious damage occurs. This works for commercial fleets as it keeps costs down. The advantage of the port at the filter for the car maker is that they don't have to listen to clueless idiots about low oil pressure. That's the main reason there are few real oil gauges in cars today. Even those that look like a gauge are nothing more than a dead ground indicator that runs at the middle of the gauge until pressure drops to less than 12lbs. Then it falls and it's usually to late for the average driver to respond to it. They're worthless at best.
Sorry, but you're making a common mistake. Oil pressure is not built until the fluid reaches the farthermost point in the lubrication system. The 5w will get there far faster than a 15w. Where you're making your mistake is if you take a mechanical gauge and put it on most car engines, the 15w will show pressure quicker than a 5w. The reason is most engines have the oil sender port right at the oil filter which is the very start of the lubrication system. What you are reading is not oil pressure but the fluids resistance to flow. Take a Powerstroke, as an example, the oil pressure sender is on the very end of the lubrication system. It may be several seconds before it reads any pressure at all. Using a 5w-40 cuts this time by a lot. Where you might see on a mechanical gauge 70lbs of oil pressure at the filter, on an engine with the oil port at the end of the lube system, you might only see 15lbs at 2000 rpms and lower at idle, sometimes as low as 5lbs. There are major advantages to having the sensor port at the end of the lube system. The biggest is that you'll know when the engine is worn and needs a basic overhaul before serious damage occurs. This works for commercial fleets as it keeps costs down. The advantage of the port at the filter for the car maker is that they don't have to listen to clueless idiots about low oil pressure. That's the main reason there are few real oil gauges in cars today. Even those that look like a gauge are nothing more than a dead ground indicator that runs at the middle of the gauge until pressure drops to less than 12lbs. Then it falls and it's usually to late for the average driver to respond to it. They're worthless at best.
If you're going to quote me, quote ALL of it. After that whole paragraph you are still wrong.
Thicker oil gives higher pressure readings. There is no debate on this. It's a fact.
I bought a jug of it at Walmart about fou years ago. I use it for the annual oil change in my push mower's Briggs engine. It burns oil if I use SAE30 or 10W30. I'm in Florida so I don't have to worry about low-temperature circulation issues. I stopped using it as my primary mower this year because I bought a rider. But, I still use it to cut the grass in the spots where the rider won't fit between trees and my fence, etc.
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