In a modern vehicle, operating temperatures are controlled by the engine design, cooling system, and load (racing, towing, etc). Operating temps are not greatly affected by hot ambient temps in the summer, but winter temps will slow down the engine warmup. The Owner's Manual takes all these factors into consideration, but they can't possibly allow for the differences between aftermarket motor oils.
Higher viscosity in summer heat??
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you guys are nuts! i have a friend with a sbc that never gets over 180 deg water and the oil temp is always 250+ he runs a 20/50 to keep it together. i know its a racecar but the principle is still the same. unless you have an oil temp guage you dont know what the [censored] is goin on and there for judging it by water temp is retarded.
back to the op, i run a 5/30 in my 5/20 spec'd engine year long and it has not blown up yet. do what you like, if you feel summer heat is too much for a 5/20 to handle with out breaking down go thicker. you wont hurt a thing!
back to the op, i run a 5/30 in my 5/20 spec'd engine year long and it has not blown up yet. do what you like, if you feel summer heat is too much for a 5/20 to handle with out breaking down go thicker. you wont hurt a thing!
Originally Posted By: Bladecutter
The bulk of you are going off the assumption that vehicles do not have some form of heat exchange taking place between the coolant and the oil somewhere in the engine.
I would bet that if the vehicle isn't designed with some form of coolant/oil heat exchanger (Like Porsche does with their liquid cooled engines), that there is an oil pressure circuit that feeds the cylinder head that goes right through part of the coolant jacket.
This would be pretty easy to develop on OHC engines too, if you think about it for a minute. That oil needs to get to the camshaft bearings in the top of the head, and the cylinder head has a lot of ports in it to flow coolant through. The oil pressure has to go through that engine block into the cylinder head somewhere, so chances are it is surrounded by the coolant flow in the head.
So even if there isn't a oil cooler on the engine block, somewhere there's a place in the engine where the coolant transfers heat into the coolant.
BC.
thats probably the most ridiculous statement i have ever read.
i ported plenty of heads in my time and never ran into an oil jacket. if its not overhead cam it doesnt even have oil ports, oil just runs off the head. if it is overhead cam the oil ports are so small no noticeable heat exchange will happen.
The bulk of you are going off the assumption that vehicles do not have some form of heat exchange taking place between the coolant and the oil somewhere in the engine.
I would bet that if the vehicle isn't designed with some form of coolant/oil heat exchanger (Like Porsche does with their liquid cooled engines), that there is an oil pressure circuit that feeds the cylinder head that goes right through part of the coolant jacket.
This would be pretty easy to develop on OHC engines too, if you think about it for a minute. That oil needs to get to the camshaft bearings in the top of the head, and the cylinder head has a lot of ports in it to flow coolant through. The oil pressure has to go through that engine block into the cylinder head somewhere, so chances are it is surrounded by the coolant flow in the head.
So even if there isn't a oil cooler on the engine block, somewhere there's a place in the engine where the coolant transfers heat into the coolant.
BC.
thats probably the most ridiculous statement i have ever read.
i ported plenty of heads in my time and never ran into an oil jacket. if its not overhead cam it doesnt even have oil ports, oil just runs off the head. if it is overhead cam the oil ports are so small no noticeable heat exchange will happen.
Originally Posted By: mechtech2
Thicker oil CAN run hotter, in certain conditions.
But not always!
maybe but i think the main concern is a thicker oil can take more heat before it doesnt lube anymore. would you agree?
Thicker oil CAN run hotter, in certain conditions.
But not always!
maybe but i think the main concern is a thicker oil can take more heat before it doesnt lube anymore. would you agree?
You're getting into the topic of shear resistance now...
Originally Posted By: dparm
You're getting into the topic of shear resistance now...
man to tell you the truth i dont know what its called but every oil and grade will only take so much heat before it fails and the rod bearings seize up. if it gets too hot to make that cushion anymore youll be buying a new motor.
i mean i cant tell ya if any car going by the manufacturer spec'd oil will ever get the oil that hot but i can tell you a 5/30 will hold film at a hotter temp than a 5/20. and a SAE 30 will hold it hotter than both for that matter.(thats why briggs recs a SAE 30 for their air cooled engines)
if i was just bent on using a 5/20 in demanding conditions such as towing in the summer i would at least go with a good syn
You're getting into the topic of shear resistance now...
man to tell you the truth i dont know what its called but every oil and grade will only take so much heat before it fails and the rod bearings seize up. if it gets too hot to make that cushion anymore youll be buying a new motor.
i mean i cant tell ya if any car going by the manufacturer spec'd oil will ever get the oil that hot but i can tell you a 5/30 will hold film at a hotter temp than a 5/20. and a SAE 30 will hold it hotter than both for that matter.(thats why briggs recs a SAE 30 for their air cooled engines)
if i was just bent on using a 5/20 in demanding conditions such as towing in the summer i would at least go with a good syn
So just stick with the viscosity the manufacturer recommends, in that case. They've selected an oil viscosity that will work in the cold of winter or the hottest summer days.
Unless you're towing a 10,000lb boat uphill in Death Valley, I think the mfg recommendation is sufficient.
Unless you're towing a 10,000lb boat uphill in Death Valley, I think the mfg recommendation is sufficient.
I run 5w-30 in the winter because the 5w flows faster in cold weather. I run 10w-30 (or some magic mix*) during the summer because the oil is not that thick in the warmer climate, and I believe that a 10w-30 has less VI than a 5w-30.
* a magic mix is oil I get on rebate like 15w-40 mixed with 5w-20 to give me a thick 10w-30
* a magic mix is oil I get on rebate like 15w-40 mixed with 5w-20 to give me a thick 10w-30
In my owners manual of my 97 rodeo it actually very highly recommends a thicker oil for summer/warm weather use over winter use.
In the winter I run 5w-30, I use to run 5w-40 in the summer, but found that it was too thick for winter use and I would never have enough mileage on the 5w-40 to call for dumping it just prior to winter.
I run 10w-30 in the summer, but honestly, I never see a difference in oil use or pressure between the two on this 3.2L Isuzu engine...it never uses more then 1/8th of a quart in 4k miles anyways.
Now in our 3.8L caravan, I most definitely see that it doesn't use any oil in summer temps as long as I use 10w-30, if I use 5w-30 it'll use a quart every 1k miles....same oil company brand.
In the winter I run 5w-30, I use to run 5w-40 in the summer, but found that it was too thick for winter use and I would never have enough mileage on the 5w-40 to call for dumping it just prior to winter.
I run 10w-30 in the summer, but honestly, I never see a difference in oil use or pressure between the two on this 3.2L Isuzu engine...it never uses more then 1/8th of a quart in 4k miles anyways.
Now in our 3.8L caravan, I most definitely see that it doesn't use any oil in summer temps as long as I use 10w-30, if I use 5w-30 it'll use a quart every 1k miles....same oil company brand.
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them old caravans aren't holding up too well are they. it seems all of them use oil and leak coolant
Originally Posted By: dparm
So just stick with the viscosity the manufacturer recommends, in that case. They've selected an oil viscosity that will work in the cold of winter or the hottest summer days.
Unless you're towing a 10,000lb boat uphill in Death Valley, I think the mfg recommendation is sufficient.
your probably right in most cases, but do you wonder if the manufacturer is recommending a 5/20 in all conditions for gas mileage rather than protection?
oil has came along way over the years tho. back in the day up north they would run an SAE 30 in the summer and then "winterize" which among other things included an SAE 20. here in the south all one needed was SAE 30 year round
So just stick with the viscosity the manufacturer recommends, in that case. They've selected an oil viscosity that will work in the cold of winter or the hottest summer days.
Unless you're towing a 10,000lb boat uphill in Death Valley, I think the mfg recommendation is sufficient.
your probably right in most cases, but do you wonder if the manufacturer is recommending a 5/20 in all conditions for gas mileage rather than protection?
oil has came along way over the years tho. back in the day up north they would run an SAE 30 in the summer and then "winterize" which among other things included an SAE 20. here in the south all one needed was SAE 30 year round
Right now my garage is at 104 degrees Fahrenheit. I've got a clear bottle of 10W-40 sitting on the shelf and if I pick it up and move it around, the oil sloshes around in there very freely. I mean VERY freely. That same oil in the kitchen freezer slows down substantially, but the oil is never going to see 32 degrees Fahrenheit inside the engine sitting inside the garage during the California summer. I'm thinking some of you guys need to VISUALLY see what temperature does to viscosity instead of just relying on a bunch of charts.
HaHa oil in the kitchen freezer..... My wife hates the idea of having to move around oil containers to make room for food come to think of it my mother did not like that either..She still does not!
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