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Question On Oil Weight

S

stuey

Full Member
Joined
Sep 14, 2002
Messages
41
Location
Livonia,MI
I have had my avy for about 3 months now and I am getting ready to change to synthetic oil on my next change.A friend of mine who owns a truck shop told me not to waste my money on synthetic, but to put in 15w40.He has had several chevy trucks over the years and gets well over 200,000 miles out of them.I'm thinking the heavy oil will decrease my mileage.If cost is not an issue what do u guys think.
 
I do what the manual states.......I see nothing wrong with Chevy's advice........
 
I've read somewhere on this site that putting synthetic oil in the crankcase and synthetic grease in the rear end gets you a fair amount of "free" extra horsepower because of the overall amount of reduced friction. ?I imagine that also gets you better gas mileage. ?If you are skeptical and don't want to spend the money to do that, then I would recommend the oil weight in the manual, which I believe is 5w30. ?The engines these days are being made with different tolerances than they were 20 years ago, and the lighter weight oils are now generally what the manufacturers are recommending. ?I've been running 5w30 mostly in my 89 Grand Prix which has had no oil-related problems and is still running well at 203 K miles.
 
I'd use synthetic before I used 15W40. 15W40 was ok in the old days when internal engine tolerances were large and gas cheap. You'll note, at least on the 5.3, the suggested oil is 5W30. Going to 15W40 will hurt gas mileage. I'm still from the old school of changing oil/filter every 3000 miles rather than letting the on-board computor tell me whe to change. 3000 miles may be overkill but I don't think it's excessive for the potential xtra margin of life it should lend to the motor.
 
It is best to use the weight suggested by the manufacturer. If you have an oil related failure and Chevy finds out you have 15w40 in your truck you could be in for a fight. I have heard stories about people running 15w40 with the theory that "thicker is better" they have a much higher incidence of cam failures. The previous poster was correct in pointing out that the newere engines are designed to run lighter weight oils. A Mobil oil engineer told me to run whatever the manufacturer says to, they have many reasons for their choice.
If you are considering running synthetic oil it is my opinion that it is worth the extra money. The lubrication properties of synthetic are far superior to any organic oil.reduced engine wear is the main reason but you also benefit from the decreased friction meaning a cooler running engine and a slight improvement in mileage.
 
synthetic question: will the oil life indicator system (if one chooses to follow it) work properly/accurately with synthetic?
 
Regarding the 203 K miles on my Grand Prix, running mostly 5w30, I changed the oil at 7500 mile increments, although it has mostly easy miles on it. I drive about 17 miles to work, 1 stoplight, 3 stop signs, and it takes about 22 minutes.
 
synthetic question: will the oil life indicator system (if one chooses to follow it) work properly/accurately with synthetic?
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I think the computer counts startups, temp reached, miles driven vs running time, etc. I don't think it actually looks at the oil or has any idea what is in the crankcase.

I picked up 1mpg by changing to synthetic in the engine.

kw
 
RichUF said:
synthetic question: ?will the oil life indicator system (if one chooses to follow it) work properly/accurately with synthetic?
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The oil life system neither knows nor cares what kind or weight of oil you have in your system. It performs no tests on the oil.
What it does is a fairly complex calculation on engine running times, and temperatures etc., to calculate when the specified grade and quality of oil SHOULD (with a generous safety margin) be in need of replacement.
It is probable that synthetic could last twice as long as the minimum specified quality. The Oil Life system will give you the same answer regardless.

I would advise switching to synthetic and following the oil life systems recommendation. Synthetic has more and greater benefits than longevity.
 
so its design basis if for regular oil then? Seems to me that it woudn't be accurate for synthetic. In other words, you'll likely be changing the synthetic oil at intervals appropriate for regular oil, but too frequent for synth. Hmmmmm. ???
 
RichUF said:
so its design basis if for regular oil then? ?Seems to me that it woudn't be accurate for synthetic. ?In other words, you'll likely be changing the synthetic oil at intervals appropriate for regular oil, but too frequent for synth. ?Hmmmmm. ????
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I don't know if I'd say TOO frequently, but more frequently than you could get away with. It think I should change my oil every 10,000, and I don't mind doing that even with Synthetic. Synthetic has other benefits....
Which reminds me,
I used to know a VW mechanic, back in the early 70's, who used to buy up old Beetles that were sound but 'running rough', and do nothing to them except drive them around and CHANGE THE OIL EVERY WEEK :eek: (Bulk oil available to him at work :rolleyes: ). About two or three months later, it would be running like a sewing machine, and he'd sell it on for a substantial profit, and buy another.
 
I would stay with 5W-30 or 10W-30 if you?re in a hot climate like I am. ?My B-in-law (service manger at a Ford dealership) has told me about engines they had to replace or rebuild because the owners used heavy oils. ?He says today?s engines are not designed for heavy oil and it is like pouring honey in your engine.

Synthetics? Well I?m running ?M-1 in two of our vehicles for better lubrication, faster flow on start, cleaner engine and the extra protection, but I don?t think that synthetics add any power. ?Mobil One DOES NOT claim to last any longer than real oil!
 
WOW!!!I want to thank all of you for the overwhelming response.You guys have confirmed my choice to run synthetic.
 
A shop I used to get inspections done at had a collection of antique oil cans. The label on the old cardboard Mobil 1 can says to change every 75,000 miles! Amsoil recommends that you change oil once a year and filter twice a year. Synthetics DO last longer than conventional.
 
synthetics maintain their lubrication properties at a higher threshold but dont neccesarily extend change intervals. Mobil is quick to say that their Mobil 1 does not extend change intervals. The only way to safely extend change intervals is through analysis. That having been said it is my humble opinion that 10,000 miles on a Mobil 1 oil change with a good name brand filter is more than adequate under normal driving conditions.
I change mine at around 6000 miles using a Purolator "pure one" filter. The climate where I live is unpredictable and I often park my truck in a heated garage. Going from a below freezing climate into a 65 deg heated garage will produce condensation.
I figure for what it costs for an oil change (buying oil on sale for around $3.99 qt) and what little time it takes to do it, I figure its a bargain vs replacing an engine.
Plus I get to spend quality time with my truck and my sons usually are more than eager to help. Last week my 10 yr old helped me swap rear springs on his moms Suburban. He still is talking about how cool that was !
 
Synthetic all the way.... I agree that you shouldn't really extend the drain interval, tho. Been using Mobil one for years in both cars and Harleys...the Harley runs substantially cooler (by my account, 20 degrees or so)...and my wife once drove a dry (a mouse ate through her rad hose) Subaru several miles. The Mobil One was black (had just changed it, too!); however, the engine was OK...I'm certain that if she had conventional oil in there it would have seized the engine! ;D
 
I have 2000 silverado and run the manufactures suggested 5w30 and it runs great. I change it every 3000 miles and have had no problems. I can't see the advantage of running a heavier oil in the newer engines. They just don't need it. I would say it would do more harm than good. I don't really care for synthtics. I just run castrol 5w30 and couldn't ask for anything better.
 
Main One said:
I've read somewhere on this site that putting synthetic oil in the crankcase and synthetic grease in the rear end gets you a fair amount of "free" extra horsepower because of the overall amount of reduced friction. ?I imagine that also gets you better gas mileage.
Click to expand...

That's pretty funny!!

Show me that data. By the way, I've got this BEAUTIFUL ocean-view estate for sale in New Mexico that you might be interested in....

Soul
 
Soul Surfer said:
That's pretty funny!!

Show me that data. By the way, I've got this BEAUTIFUL ocean-view estate for sale in New Mexico that you might be interested in....

Soul
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IS SYNTHETIC OIL REALLY WORTH IT?
ALL FACT, NO FRICTION -- August 2002

"It's pretty amazing when you think about it -- all those metal parts spinning away furiously but never making contact. Oil makes it all possible... a gain of 10.1 hp and 6.1 lb-ft just by switching to synthetics...in our opinion, they're worth it for cars you car about."

Hot Rod Magazine

Hot Rod Test Article Showing a 10.1 HP gain

So...where's that property Chris ?
 
Do not go to 15W40 oil. It would be a mistake. The worst potential damage done to an engine is cold start-up and failure to properly circulate oil quicly throughout the entire valvetrain area. 5W30 is recommended to aid in the quick lubrication and to ensure that the proper circulation is obtained quickly.

It is a violation of warranty to place this oil in the engine. The manual calls for 5W30 throughout the entire temperature range with 10W30 as acceptable if the temperatures never go below zero f. The manual specifically states " DO NOT USE 20W 50 OR ANY OTHER GRADE OIL NOT RECOMMENDED."
 
The most important thing you can do in choosing oil is to pick the correct viscosity according to the manual. In all of my family's gas vehicles I run 5w-30.

Switching to synthetic made my engines run noticably smoother and quieter. It's definitely worth the money especially considering that you can extend your drain intervals with Amsoil. Amsoil advises 25k drain interval with a filter change and top off oil at 12.5k.

The GM oil life monitor only monitors your driving conditions to calculate when to change the oil. Of course, you can drain the oil when the monitor tells you to but it's not absolutely necessary with Amsoil. I use the oil life system to tell me when to change the filter. Then I reset it and once it goes to 0% the second time, I drain the oil.
Thomas
 
:) We started using synthetic 5w50 Castrol Syntec---the 8.1 liter eng went thru it at 1 plus quarts per 1000 miles---switched to 10w30 synthetic and in 3000 miles almost no oil used at all.

Possibly 5w30 might have been ok--but the 10w30 falls into the specs range for this climate on the west coast--for all seasons.Think we will stick with the Castrol 10w30 synthetic.For the first 4000 miles we used dino 5w30 and no oil burning at all--odd for this RAT motor--would have thought we would burn some during the break-in period for the first 3000 miles.

No real diff in the oil flow time or the engine rattle--piston slap--on the 8.1 l engine--no matter what oil we used--poss in the winter at minus 20 temps it would be important and 5w30 would be of great benefit.

Finally settled on15w50 syn mobil one---the only oil that goes over 2000 miles without radical oil burn--and is consistant--some of the 5w30 would burn a qt in 600 miles towing in the mountains!It never goes outside the Generals 1qt ./ 100 gallons of gas--so can't qualify for a rebuild!!For such a recent technolgical engine it makes me wonder???The most frustrating engine I have ever owned--guess we were spoiled by the 5.7 liter!!

Clare
 
Oil does not "wear out" whether it is synthetic or conventional. The reason that oil is changed is because the additive package is used up and contamination happens. Oil contains additves that provide protection against acid build up and these eventually are used up. Water and other contaminates build up in the oil from condensation and the by-products of combustion. This contamination varies with the type of driving that you do. Longer distances are easier on the oil than low speed, stop and go driving. I will use a synthetic oil for the benefits of better protection and higher gas mileage, rather than trying to save a few dollars per year by extending my oil change intervals.
Also the use of heavier oils dates back to the days when engines were much cruder that those we have today. The clearances are much tighter and highly machined than back in the old days. It is much more important that oil flow freely, especially when the engine is cold, than to try to fill the "gaps" from sloppy machining with thick oil.
 
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