Good oil change interval?

[Addicted To Boost]

the motor suggestions running 10w30 in the summers and the recommended 5w30 in the winter.

That's a terrible idea... not sure where you heard that. The first digit in the 5W30 multi-viscosity rating, "5" is what weight the oil acts like at room temperature. The second digit "30" is the weight the oil acts like at operating temperature ~210*F. You want a very low viscosity for startup protection when the engine is cold and the most wear takes place. The second number really depends on application. In our cars, there is no need to run anything more viscous than 5w30.

[GnatGoSplat]

I always run 10W30 in the summer and 5W30 in the winter. I use 5W in the winter for the startup protection in the cold, but I switch to 10W in summer because the low viscosity is not needed and 5W30 has more viscosity improvers. I'm sure 5W30 is fine all year round and probably viscosity improvers have gotten better, but years ago I had read it's better to have less viscosity improvers and 10W30 has less than 5W30. That, and avoid Fram oil filters, are probably the only "oil paranoia" things I subscribe to.

[gr8shot]

Im on pace to put 30k on my cutlass in the first 12 months of owning it just commuting to work. Not counting errands and other stuff. That's $600 a year in oil changes if I changed it every 1500 miles. $225 if I change it every 4000 miles like I plan to. $180 @ 5000 mile changes. Spending even $75 for 3 oil analyses to find my best OCI is money well spent when a person puts on the miles that I do. If I find out I can safely go 5000 miles, even spending that $75 for analysis I still save almost $50 by going from 3k to 5k. Plus I have plenty of piece of mind (oil analysis) that my motor is in good shape. Seems like a no brainier for me.

Sent from my old skool Droid

[RobertISaar]

In our cars, there is no need to run anything more viscous than 5w30.

i ran a couple bottles of 20W-50 for shits/giggles once in the 3100.... yeah, totally bad idea. you'll have ridiculous oil pressure at all times, but damn does it drag down the motor.

I always run 10W30 in the summer and 5W30 in the winter. I use 5W in the winter for the startup protection in the cold, but I switch to 10W in summer because the low viscosity is not needed and 5W30 has more viscosity improvers. I'm sure 5W30 is fine all year round and probably viscosity improvers have gotten better, but years ago I had read it's better to have less viscosity improvers and 10W30 has less than 5W30. That, and avoid Fram oil filters, are probably the only "oil paranoia" things I subscribe to.

FRAM = FAIL

but we all knew this.

and yes Shawn, less viscosity improvers to meet a certain rating is good, since they do wear out/deplete, causing the oil to thin out a lot less than it's original rating.



best of all worlds: a cheap(yet still great) full synthetic. synthetics have significantly fewer viscosity improvers, along with a bunch of other benefits i'm not going to ramble about, since there is already plenty of info available already via google. however, finding the best synthetic for the money is almost as much art as it is science.

and since it was mentioned, GM makes references to the older oil life systems going up to at LEAST 7500 miles, when driven in perfect conditions. 10,000? i've never seen it, but maybe a DIS on a testbench would be a good idea...

and i double-checked the 95MC owner's manual: 7500 in normal conditions, 3000 in severe duty.

[Schurkey]

Bringing this back from the dead.

http://hbassociates.us/Oil_Analysis_1.jpg
(Click on image to enlarge)

While not directly applicable to a W-body, here's an oil analysis record from my Trailblazer with the 4.2 DOHC inline six. The form used specifies that the "Time on Oil" is in hours, but the figures are actually in miles. The far right column is the oil sample taken when we bought the vehicle at ~24,000 miles. I have no idea how long the oil was in there, or what brand of oil it is.

Middle column is a sample taken with "typical" use for this vehicle. The Oil Life Monitor has typically allowed about 13,000 miles between oil changes. At that mileage, (13,000) this (Mobil 1 5W30) oil was still fit for further use. I use NAPA/Wix filters.

First column is most recent oil change. In fact, the report showed up in the mail yesterday. I intended to dump the oil while on a trip to California/Arizona. I ran out of time at my Dad's place in California, and my Father-in-law in Arizona isn't allowed to touch a wrench at his retirement community or he gets thrown out for violating Park rules--so I just drove back home; exceeding the Oil Life Monitor's recommendation by about 1,500 miles.

Even with 15,000 total miles since the last oil and filter change, and 117,000 miles on the vehicle...the oil is fit for further service (I changed it at the time the sample was taken.) I think I had to add two or perhaps three quarts in that 15,000 miles.

Dumping oil at 3000 miles on a feedback-fuel-injected, overdrive-transmission-equipped vehicle in otherwise good condition and not operated under "severe" conditions is NUTS.

[pitzel]

Yup, precisely. I have run the past 100,000km on 2 oil changes. One at the 100k mark when I got the vehicle, and one at 158k when the LIM leaked and I had to re-do it. Now I'm just cracking 201,000km, on my second oil change.

The engine was spotless internally when I pulled the LIM apart to do the gasket. After 58,000 km (36,250 miles) on Mobil-1 and Esso XD-3 0W-30. The whole idea of changing oil, IMHO, is insane, especially when you have a filter to keep it clean. I do change my filters once every 15k miles or so. And keep the oil topped up. I bought 4x4L and 12 x 1L bottles (28L) of XD-3 0W-30, and if you subtract one full oil change (5L), I've consumed 13L. And most of that leaked out of the engine, with probably 3L just for make-up on the filter changes. So roughly 1L of oil consumption/leakage every 10,000km.

[pitzel]

Schurkey, its too bad you weren't able to get TBN and oxidation numbers for the oils on the chart. Although I suspect that, in the 3.1L engines, as long as the coolant is kept out and the fuel system isn't badly out of tune, oil could literally last forever.