engine oil viscosity

chaos254

Founding Member
Jul 27, 2002
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NJ
I've been running 10-30w mobil 1 synthetic in my mustang since I've owned it but I'm wondering what does everyone else run? My chilton books says engine oil viscosity depends on operating temperature range. Well I live in the Sacramento, CA area and in the summers we reach temps of ~100-110 F and the lowest in winter we normally see is around 30. Should I be running a thicker viscosity oil? What are the difference in oils? Any benefits of running a thicker oil compared to lighter?
 
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I've been running 10-30w mobil 1 synthetic in my mustang since I've owned it but I'm wondering what does everyone else run? My chilton books says engine oil viscosity depends on operating temperature range. Well I live in the Sacramento, CA area and in the summers we reach temps of ~100-110 F and the lowest in winter we normally see is around 30. Should I be running a thicker viscosity oil? What are the difference in oils? Any benefits of running a thicker oil compared to lighter?
I'm in Fresno and I run a 10W30. That's what's recommended by Ford as per my owners manual... Yes, I still have the owners manual... lol
 
Personally I use 10w-30 Castrol GTX and always have. I have been considering switching to royal purple though, but a quart is $9 here and that can get pricey.

Here's a comparison in sorts.
Thin Oil - Good start-up protection, cooler oil temps, good fuel efficiency but potential for engine wear if you push your engine to extremes.

Thick Oil - Can make the engine feel sluggish, higher oil temps/pressure, more stable to fuel dilution and more protection for the engine.
 
With my bearing clearances and turbo I run 20w50 and I like Royal Purple all I run.

I ran Castrol GTX for years before swapping to the RP. Always ran 10w30 when my motor was stockish.
 
While we're on the subject... the guy who put my turbo in said i should run 15w-40 in my car since I put the turbo in. Does that sound right? They all say diesel oil. btw the motor is pretty much stock besides the turbo
 
I know lots of guys that run that oil, it's dirt cheap also!
I run the 20w50 based more so off my bearing clearances and what my machine shop recc's. Also Royal Purple recc's 20w50 for drag racing/forced induction cars.
 
should you use the same viscosity oil in a brand new engine as you would in one with high mileage?

also, for an older car with upwards of 100K miles on it, is it OK to switch to synthetic?

i will be changing the oil in my wife's cabrio soon and it has 90K miles. i'm just wondering if i can safely use synthetic, and if i should use the recommended viscosity or something a little thicker (or thinner) because of the age of the engine ...
 
You really want to run the thinnest oil you can get away with. 10W-30 generally works fine on a 5.0. More modern engines run a thinner oil because the engines have tighter tollerances. As the engine gets older, and some things start to loosen up, you will need a thicker oil to fill in the gaps.

Ever wonder where it comes from?

Oil viscosity is rated as such. The first number is the viscosity at normal operating temperatures. (The 10 in 10W-30). The second number is the viscosity when it is cold, hence the 'W' for winter.

Oil viscosity is measured with a tool called a Saebolt viscosimeter. Oil at a given temperature is poured into a funnel with a fixed orifice at the bottom. The time it takes for a given volume of oil to drip through that orifice is measured in seconds, now referred to as Saebolt seconds. That number is then divided by 10, and again by 2 for cars. Airplanes you just divide by 10. So if it takes 1000 seconds for it to drip through the viscosimeter, that would be 100 weight oil for airplanes, and 50 weight oil for cars.

Kurt
 
Oil viscosity is rated as such. The first number is the viscosity at normal operating temperatures. (The 10 in 10W-30). The second number is the viscosity when it is cold, hence the 'W' for winter.

It's actually the other way around. The first number with the W is what the oil viscosity is at 0°F, the second number is at 210°F.

A vehicle's oil has to be thick, but not too thick. It is important that in the winter, the oil be thin enough to allow for the engine to start. But when the engine is warm, the oil must be thick enough to lubricate properly. That's where the numbers come into play.

Neither number corresponds to an actual 'weight,' even though that is the term most people use when referring to motor oil. The viscosity (flow resistance) is tested by allowing a small amount of oil to flow through an aperture. The quicker the oil flows, the lower the rating numbers.

The first number rates the viscosity of the oil at a temperature of 0 degrees F, mimicking cold winter weather, which is why the 'W' designation is added at the end of the first number. The second number repeats the test at 210 degrees F., or normal operating temperature for a fully-warmed engine.

The 'W' rating can be 5, 10, 15 or {20;} lower numbers mean the oil is thinner in cold temperatures, necessary for icy climates. The second number rating (meant to represent normal operating temperature of an engine) can be 20, 30, 40 or 50. Warm-weather spots usually require oil in the upper end of that range that can handle extreme heat.

On that note, I run 5w-30 Mobil 1. :D
 
^ and ^^ Very great info! Never knew any of that.

My stang has a little over 94k on the clock, all stock, and I run 10W-30, used to be Royal Purple but now it's Mobile 1 because of a killer deal we've had locally on it - $29.99 for 5 quarts plus Mobile 1 filter!
 
should you use the same viscosity oil in a brand new engine as you would in one with high mileage?

also, for an older car with upwards of 100K miles on it, is it OK to switch to synthetic?

i will be changing the oil in my wife's cabrio soon and it has 90K miles. i'm just wondering if i can safely use synthetic, and if i should use the recommended viscosity or something a little thicker (or thinner) because of the age of the engine ...

I'm pretty sure that the whole can't switch to synthetic after a certain amount of miles is a myth. I'm switching my daily driver(96k) and my fiances vehicle(112k) to synthetic just because I'm lazy and can go longer without oil changes. If they both blow up i'll let you know.. lol

I was at the store today and I thought about using royal purple but I just couldn't justify paying 9.00 a quart for it. Especially when Mobil 1 synthetic is half of that and I've never had any issues with it.
 
I'm pretty sure that the whole can't switch to synthetic after a certain amount of miles is a myth. I'm switching my daily driver(96k) and my fiances vehicle(112k) to synthetic just because I'm lazy and can go longer without oil changes. If they both blow up i'll let you know.. lol

I was at the store today and I thought about using royal purple but I just couldn't justify paying 9.00 a quart for it. Especially when Mobil 1 synthetic is half of that and I've never had any issues with it.


It was my understanding that it wasnt about anything blowing up. Its about the rubber seals swelling due to dino oil and then going back to their regular size with synthetic.....so the "myth" was that if u switch with high mileage that you will get oil leaks.


Cant hurt to try.
 
once i find an oil that works... i dont change...

Ive been using the motorcraft synthetic blend in my focus and my g/fs focus... my grandfather uses it in his honda and f150... My cars never burned oil or started to even after putting 40k on the focus... i dont lose a drop..:nice:


The only oil i have ever had problems with was quaker state and i think Pennzoil

I was using quakerstate in my probe... and look at it...
DSCF0872.jpg

DSCF0871.jpg

cleaned out gunk... flushed and used gtx...
DSCF0917.jpg

I think thats much better...

My mustang had 225k+ on it when i pulled the engine to clean up my bay... you should of seen how clean it was under the VC's
 
It was my understanding that it wasnt about anything blowing up. Its about the rubber seals swelling due to dino oil and then going back to their regular size with synthetic.....so the "myth" was that if u switch with high mileage that you will get oil leaks.


Cant hurt to try.


I know, I was just joking about it blowing up. It seems like there are both sides to it. Some people say it causes leak and others have switched with no issues. So who knows..