Heavy vs Light Weight Oil in High Mileage Motor

[landtoy80]

In a motor with very high mileage would there be any difference in power (pulling a steep hill) in cold weather (below freezing) between a 5w30, 5w40, 15w50 and a 5w50? Would there be much a change in mpg? Common knowledge says to use a heaver oil for older motors but I have searched that the heavier oils leave a film in the cylinder and get burned off. IF so, would that extra oil in the cylinder mess up the fuel ratio and cause less power?

 

[daman]

Well a thicker oil will cause more rotating drag and slower cranking rpms especially in cold temps ,so imo stick with the recommended viscosity,my '99 z71 has 235,xxx and i run 0w30,5w30 no problems good oil pressure too. never heard anything like that about your last question..

 

[Astro14]

My '90 4Runner has 226K on it...doesn't need a high viscosity oil (10W30 or 10W40 or 5W30 was recommended, depending on temperature). The real question is: what's your pressure when the engine is at operating temp? IF it's low, bump up the viscosity a bit...I run a 5W40 summer, when the truck is taken 4 wheeling and is run hard, 5W30 for Vermont winters, and 10W30 for Virginia winters and the pressure is good... The real question in cold weather is the start-up, if it's cold, go with a 5W, or better, a 0W...and if you use a really heavy oil (e.g. 15W50)...you'll increse the drag on the motor and cause a noticeable loss in power without gaining anything but harder starting and worse mileage... Once the engine is warm...it's warm...and the oil temp will be pretty close to the coolant temp...and the recommended viscosity should be fine... So, for Grand Junction, I would try a 0W30 or a 5W30 this time of year for those cold mornings...and if, and only if, the pressure at a hot idle is low, then I would go 5W40 or a 0W40.

 

[mechtech2]

Lighter oils will allow more power and fuel economy. So we generally use as light as we can, while still protecting the parts. there is no connection to the fuel mixture unless you are burning a lot of oil.

 

[landtoy80]

<<>> About 8 years ago I tried using M1 oil in my 94 Land Cruiser with 210,000 miles on it. I would burn oil at a qt per 100 miles if I ran it hard. Burned it not so fast if normal driving. Switched to Rotella T 5w40 synthetic and ran it hard and on oil added for 3000 miles. Reason I ask is I normally run Vail Pass in Colorado (steep climb) and my speed would drop to 60 mph with my foot to the floor all the way up the steep part. One day I ran up the pass with about 10000 miles (added 8 qts of oil over 10000 mi) on the oil and the speed dropped to 60 mph. One day later with the same temp (about 30 F) and conditions I pulled the pass and the it dopeed to 45 mph. The only thing I did was switch to M1 15w50 and a can of Restore. Could fresh 15w50 and additive slowed down the motor that much? Ever after I could only pull the pass at 45 mph. Switched to Toyota/Chevron 5w30 and pulled the hill and the speed was back to dropping to 60 mph. Nothing else was different, same weight of cargo in vehicle. I think my oil gets diluted with gas over time so it may be thinned out. The guys on the Land Cruiser forum say the oil could not be the problem. Was it just a coincident that my speed dropped with the heavy oil?

 

[Merkava_4]

Originally Posted By: landtoy80

Common knowledge says to use a heaver oil for older motors but I have searched that the heavier oils leave a film in the cylinder and get burned off. IF so, would that extra oil in the cylinder mess up the fuel ratio and cause less power?

You're not supposed to get oil in the combustion chamber unless your piston rings or valve guides are shot. Which engine are we talking about ?

 

[45ACP]

Originally Posted By: Merkava_4

Originally Posted By: landtoy80

Common knowledge says to use a heaver oil for older motors but I have searched that the heavier oils leave a film in the cylinder and get burned off. IF so, would that extra oil in the cylinder mess up the fuel ratio and cause less power?

You're not supposed to get oil in the combustion chamber unless your piston rings or valve guides are shot. Which engine are we talking about ?

You are referring to the walls of a cylinder not becoming "washed," meaning having no oil, which can lead to failure, which is what you want to avoid. When you tear an engine down, the parts have an oily film on them. The oil still needs to flow from the bottom to the head, which is why a thinner oil at startup is best and the days of 10W are dead. 5W or 0W ONLY now. Group V oils like Redline are said to somewhat "stick" to the parts better, and its something id consider if i ever become ok with getting my oil in the mail. I just may never go back to Walmart if that happeens. For oil. I dont know. Its hard to say, the 5W still flows pretty quick. its