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Synthetic vs mineral oil

Juice3

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I know synthetic oil is better than mineral oil but my vx runs way smoother on castrol 15w 40 mineral than it does on penrite fully synthetic 10w 50 idk if its because the penrite is thicker or not but i can notice a big difference using the 15w 40 car feels sluggish on the 10w 50
 

losh1971

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I thought the 15w was thicker than the 10w. Doesn't the W mean winter weight? I use a 20w 50 as the 20 is thicker than a 15w 50.
 

Juice3

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I thought the 15w was thicker than the 10w. Doesn't the W mean winter weight? I use a 20w 50 as the 20 is thicker than a 15w 50.

Not sure I thought the first number is how thick the oil is at startup.
 

Juice3

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Found this on valvoline website

The "w" in motor oil stands for winter. The first number in the oil classification refers to a cold weather viscosity. The lower this number is, the less viscous your oil will be at low temperatures. For example, a 5W- motor oil will flow better at lower temperatures than a 15W- motor oil. The higher number, following the “w” refers to hot weather viscosity, or how fluid your oil is at hot temperatures. The higher the number, the thicker the oil at a specified temperature.
 

losh1971

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I haven't researched it much. When I was young Valv XLD was one of the best oils available at a reasonable price. Mob 1 was around but was 80 bucks for 5L. 20w 50 Valv was still considered expensive but the cheaper options were Mob Super or Black and Gold but only women used that gear. I use 20w 50 in the Buick because the mech said I need a thick oil due to the age and mileage of the engine. Yet I used to run 5w 40 in the XJ 4.0 and it clocked up over 300k and still didn't use anymore than 500mls between 10k changes.
 

Juice3

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Yeah I think i'm going to switch back to a 15w 40 oil because car just feels so much smoother on it I have been using the 10w 50 for about 3 oil changes now and it just makes the car feel sluggish.
 

losh1971

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What's your ride? If its a VT or something with an Eco, I'd be running 15w anyway.
 

1985VK

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Synthetic oil is usually oil that has been processed so the hydrocarbon chain lengths of the molecules are more consistent... "synthetic" does not necessarily mean "artificial" ...
 

07GTS

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a slightly thinner oil may have more of its volume going thru the bearings making it smoother where the thicker is at a slightly higher pressure but the volume might not be as good, it also depends on your clearances, also film strength plays a big roll as thickness wont matter if the oil cant hold itself together under the operating loads
 

Calaber

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The grade of oil used should also take into consideration the distance the engine has travelled. Higher mileage means increased wear and greater tolerances between moving parts, making heavier grade oils more appropriate to maintain satisfactory oil pressure and more cushioning lubrication to bearings than thinner oils.
 
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