5w30 too low viscosity?

[VadersV6]

My point is, decide on an operating temperature of your engine...oil and coolant. Decide, hyper pistons or forged? What will break a hyper piston will usually break a forged one too....hint...hypers arent as bad as you think and you dont need forged unless you're crazy fast.
If you go forged anyway, dont go as big on clearance as they recommend, run the motor cool, and you wont have that catch 22 with cold weight and hot weight, cold clearances / hot clearances. Do you plan on a full boost 1/4 mile pass with the motor at 60 degrees? I sure hope not, so why would you care about the cold weight anyway? They want to design an oil where in case you do decide to load the motor when its cold, the cold viscosity will cover it. But you should always warm your motor and especially turbo up before going WOT, and straight weight oils tend to have better additives for our flat tappets....just run proper clearances, warm the damn engine up before driving it, run a 5w-30 with hyper pistons (with proper, p/w tight clearances(.001-.0015) and 10w-30 with forged pistons with slightly larger clearances. (.0025-.003) and run the motor cool. If you run the motor at 200+ degrees, go with the recommended, forged piston P/W clearance and run a THICK oil.....you know, the way they did it back in the 50's and 60's when they didnt know WTF they were doing yet.

 

[BlackBandit]

Let me start my explaining that the W in multi grade oils represents the word winter. Not weight, an idea I previously (and recently:redface: ) subscribed to until a board member here was kind enough to point out my ignorance. That said I think I see where the disconnect is. You don't measure an oils ability to flow (viscosity) by the "weight". You determine an oils weight by it's viscosity at a certain temperature. They did not start making multi weight oils because of cold clearances. They started making them because they could. It might help to think of it like this. The second number of an oil is how it behaves at operating temperature. The first number is how it behaves when cold. A 5w-30 oil is an oil that thickens up to a the same viscosity as a 5 weight oil when cold. A 5 WEIGHT OIL IS WAY TOO THICK TO PROTECT AN ENGINE WHILE COLD. However, when a 5 weight oil gets warm it's TOO THIN to protect an engine. For this reason they add viscosity index modifiers that prevent the oil from thinning beyond a certain point. (the second number) So if you heat a 5w-30 and a SAE 30 weight oil to 212f they will behave the same. If you cool them to freezing the 5w-30 will behave like a 5 weight oil (meaning it will still pour) and the SAE 30 will behave like a 30 weight oil. (meaning it will be almost a brick) Both would fail to provide adequate protection while cold, the 5 weight oil would just do a better job.

This may make it sound like it's a no brainer to go out and buy 0w40 oil and call it a day. It's not quite that simple though. See, the the only way to get a oil to behave like a light oil in winter conditions is to use a lighter base stock. This is the oil you add the viscosity index modifiers (or viscosity index improvers. VII's) to. The problem is as you use an oil those VII's break down and your oil reverts back to it's "natural state". The the wider the gap between the winter and operating weight of the oil the longer and more fragile the VII's needed become. This causes the oil to breakdown more quickly requiring more frequent oil changes. The more severe the operating conditions the more quickly this will happen. Not a big deal if you change the oil, but eventually that 0w-40 is going to revert back to almost a 0 weight oil when hot and your oil pressure would then be almost non existent. This is probably why OEM's don't just arbitrarily recommend the lowest base weight oil possible for a car. They have to take into account the abuse that will be put on an oil and balance that with people not wanting to do a ton of maintenance on there cars.

Renthorin, sorry for the off track these posts took. Leave the 5w-30 in there and call it a day. If you get your desired pressure you'll end up with more protection as a 30 weight oil will flow more at the same temp/pressure than a 40 weight oil. This will provide your bearings with more cooling.

 

[VadersV6]

Let me start my explaining that the W in multi grade oils represents the word winter. Not weight, an idea I previously (and recently:redface: ) subscribed to until a board member here was kind enough to point out my ignorance. That said I think I see where the disconnect is. You don't measure an oils ability to flow (viscosity) by the "weight". You determine an oils weight by it's viscosity at a certain temperature. They did not start making multi weight oils because of cold clearances. They started making them because they could. It might help to think of it like this. The second number of an oil is how it behaves at operating temperature. The first number is how it behaves when cold. A 5w-30 oil is an oil that thickens up to a the same viscosity as a 5 weight oil when cold. A 5 WEIGHT OIL IS WAY TOO THICK TO PROTECT AN ENGINE WHILE COLD.

5 is the oils weight at operating temperature. W-30 is the weight when cold.
Its not 5W, and -30. Its 5 and W30. You need the 30 (thickness, adhesion, etc) when cold to suspend the main journals in the main bearings, rod journals in the rod bearings, pistons in the cylinders....when cold, and the "gaps" are large. (measure a main journal on a crank in winter, and measure it in summer...with a good micrometer) The gaps get smaller as the temps increase and the oil needs to thin out to fill the gaps and continue to suspend the spinning/reciprocating components. A 5 weight oil IS too THIN to protect an engine when cold. Not too thick.

 

[87natl]

Off my recent rebuild, after break in, My engine builder suggested I go synthetic 20-50W. Well, as soon as I did that, once the engine got warmed up I got valvetrain noise. I switched to a straight 30W and she's quiet as a church mouse. Figgur dat!

 

[turbofrank]

You are ok . Mich burrr cold when i lived there i think 5-15 or 5-20 was winter oil. My cars thanked me for it

 

[BlackBandit]

5 is the oils weight at operating temperature. W-30 is the weight when cold.
Its not 5W, and -30. Its 5 and W30. You need the 30 (thickness, adhesion, etc) when cold to suspend the main journals in the main bearings, rod journals in the rod bearings, pistons in the cylinders....when cold, and the "gaps" are large. (measure a main journal on a crank in winter, and measure it in summer...with a good micrometer) The gaps get smaller as the temps increase and the oil needs to thin out to fill the gaps and continue to suspend the spinning/reciprocating components. A 5 weight oil IS too THIN to protect an engine when cold. Not too thick.

Yes, metal expands when heated. This doesn't have that dramatic of an effect on clearances. I don't want to be a dick or anything but everything else in this statement (and allot in the previous ones) is false. I would encourage anyone reading this to do a simple web search on what 10w-30 stands for and then come to your own conclusions about what advice in this thread is worth taking. Sorry Vader, but these are the types of statements that perpetuate bad information and send multitudes of people off to make bad decisions that ruin cars. Please don't take it personal. james