OT Oil Life Index

I recently purchased an '06 Chevy Trail Blazer with On Star. I changed the oil when I got it home and reset Oil Life Index back to 100% and it was confirmed on my account on my computer. After 3000 miles of driving I checked my On Star account on my computer and it said my Oil Life Index was still at 94% and my next oil change was due at 49,500 miles. If I let it go that far, there will be 13,500 miles on the oil. This seems excessive to me. I realize I can change the oil as often as I want. I also realize GM wants repeat customers after wearing out your vehicle. I have always been a maintenance nut. I was thinking of changing at about 6 or 7000 miles. It has the 4.2 L  inline 6 cylinder engine and it takes 7 quarts of oil with the filter. I use Full synthetic oil and change the filter every time myself. The truck is driven in Central Vermont and does not get driven on short trips. With the price of oil these days, it makes you wonder if you might be going overboard. What do you guys think? Thanks in advance for your input.

The new oil life indexs base off engine rpm and run time and other varibles to driving.

On my 99 silverado 6.0 liter. I think the thing works fairly well. If im pulling the gooseneck alot it goes of around 3000mi if not its been upto 6000 b4 it has went off and said change the oil. Rite now the silverado has alittle over 198,000 miles never touched the engine and its still strong

The oil companies have perpetuated the 3000 mile myth for so long that many belive it.  In modern engines, with modern oil there is not reason to change at 3000 miles.  Don't believe me, send a sample into the lab for a test.  Air filter/intake systems have come a long way and seal/filter much better than the days with the filters bolted onto of the carb.  Fuel injection systems prevent fuel dilution due to sticking needle/seat or rich running carbs. 

On the other hand, the manufactures have been pressed to extend their oil change intervals for "environmental" reasons.  The general population might be well served by these recommendations but certain groups should change theirs somewhere in between.  Most on here live near or on farms which means more dust, and use their vehicle for work(the general population doesn't) 

Aftermarket filters such as the K&N should change the oil at 3000 miles as you are sucking more dirt into the intake. 

Our hoof trimmer changes his 7.3 Powerstroke every 10-12k with synthetic.  Going on 300,000 now.

3 to 5,000 miles for me depending on the vehicle.

My 05 Merc. has that also but in percentages it goes off between 3 and 4 thousand. I wouldn't let it go any further than 5 thousand because like motorheads say I want the engine to last awhile. Funny thing about the car is it uses 5W20 but I have 111,000 on it and it doesn't use a drop inbetween changes.

 Send a sample of your drained oil to a lab for analysis. With a synthetic and 7 qt. of capacity , I would change at 7500 or 8 thou, unless the monitor recommended sooner.

Brian Jasper co. Ia wrote: Theres no myth about it. Why do you change oil? Is it worn out? No, it's DIRTY. You change it to get rid of the contaminates. Those contaminates are what causes wear. Those contaminates are what build up and plug the screens in things like cam phasers.

Did you read my reply Brian?  I mentioned nothing about wearing out.  I talked about fuel dilution and silicon contamination(dirt). (Multigrade Dino oil does oxidize but not any where near 3000miles)  These things just don't happen in modern fuel injected vehicles in good condition at 3000 miles.  Yes they were applicable to older carburettor equipped vehicles, but since we are talking oil life index equipped vehicle, 3000 mile oil changes are unnecessary.  I have never seen an oil sample come back recommending chance at 3000 miles, except for two reasons, one was a coolant leak and 2 was a vehicle with a tear in the air intake hose. 

Brian Jasper co. Ia wrote: Take my advice and change at 3k for ordinary oil, no more than 5k for semi synthetic.

Can you explain to me how regular oil gets "dirtier" quicker that semi synthetic? The type of oil has nothing to do with particulate contamination, nor fuel dilution, nor moisture.  Even modern dino oils won't begin to see appreciative oxidation at 5000 miles. Contamination is a result of the efficentcy of the air filters(which is upwards of 96 percent with modern rectangular pleated filters) the crankcase ventilation system, and malfunctioning equipment.

So exactly why can you go 5000 miles on semi synthetic but not standard oil????

Well Good, there are many variables to consider.  The hotter the engine runs(which propane engines do run a little hotter) the faster the oil oxidizes.  Also the enviroment that it runs in and how well the air filter(intake is the largest source of dirt) is a big factor. 

The engines I work on go in some of the largest mining equipment in the world.  These are 3000hp+ diesel engines with 150 gallons+ of oil depending on model/application.  These mines operate 24/7 364 days a year and never even shut down except for major maintenance.  They don't even shut down for fuel/driver changes.  When refueling, the service truck hooks up an oil polisher that circulates oil from the truck and filters through 2 micron filters and through high quality cotton bypass filters to take carbon black out and other sub micron particles.  Some mines use straight 30W dino oil.  Multigrade oils break down faster but provide much better start up protection, but since these machines are never shutting down, that is not an issue.  If using dino oil they will at intervals pump a few gallons of oil into the fuel tank after its polished and make up a few gallons with new to refill.  Pretty much replacing all the oil once a year.

The mines running synthetics never change oil as they don't break down.  The important part of all this is the oil sampling.  Done right the can tell you with pretty good accuracy what is happening in an engine and tell you well in advance on impending failure.  Some of these engines have special double filter units that you can shut down the main filters while the engine is running and replace them without ever shutting down.  This is a very common item on the engines going into ships as well.  Ship engines have very long oil life due to the low dirt content in the air, consistent load, and consistent temps.  Some ships also use the polishers as dealing with oil changes can be a very big problem on boats

On a personal note.  I have a truck that I used to have a set of bypass cotton filters on it and changed the oil every 25000 miles but check the oil at 12500 by oil sample analysis.  It has 280000 miles and never been opened up.  I did eventually take them off because the company that made them (Amsoil) raised their prices so high that it was not cost effective especially now that I don't drive it very much(its the farm beater truck now) especially for 6 quart capacity.  Now on a large truck with several gallons of oil capacity, it would be worth it monetarily.  Setting/short operation times or infrequent operation promotes water condensation and you need to change the oil even if it hasn't run that many hours/miles just to remove the water in the oil and prevent acids from forming. 


Edited by firebrick43 - 05 Nov 2010 at 12:55pm

You guys about have me sold an synthetic oil.Do the old nonfiltered big briggs and stratton like the synthetic?

firebrick43 wrote: Brian Jasper co. Ia wrote: Theres no myth about it. Why do you change oil? Is it worn out? No, it's DIRTY. You change it to get rid of the contaminates. Those contaminates are what causes wear. Those contaminates are what build up and plug the screens in things like cam phasers. Did you read my reply Brian?  I mentioned nothing about wearing out.  I talked about fuel dilution and silicon contamination(dirt). (Multigrade Dino oil does oxidize but not any where near 3000miles)  These things just don't happen in modern fuel injected vehicles in good condition at 3000 miles.  Yes they were applicable to older carburettor equipped vehicles, but since we are talking oil life index equipped vehicle, 3000 mile oil changes are unnecessary.  I have never seen an oil sample come back recommending chance at 3000 miles, except for two reasons, one was a coolant leak and 2 was a vehicle with a tear in the air intake hose.  Brian Jasper co. Ia wrote: Take my advice and change at 3k for ordinary oil, no more than 5k for semi synthetic. Can you explain to me how regular oil gets "dirtier" quicker that semi synthetic? The type of oil has nothing to do with particulate contamination, nor fuel dilution, nor moisture.  Even modern dino oils won't begin to see appreciative oxidation at 5000 miles. Contamination is a result of the efficentcy of the air filters(which is upwards of 96 percent with modern rectangular pleated filters) the crankcase ventilation system, and malfunctioning equipment. So exactly why can you go 5000 miles on semi synthetic but not standard oil????

You might want to give some thought to suspension and additive packages...

In 1974 I worked for a trucking comany.  Everupme was looking for advice on oil changes as the cost of the oril change had dramaticaly increased due to the oil crisis.

When I had my FedEx Home Delivery truck, I had to go to Freightliner (they had the warranty) to get an explanation of my owners manual.  I had to have a maintenance plan on file with FedEx, and they would not believe how many miles they were allowing between changes.  I was driving as many as 350 miles per day, 5 days a week, and at the 5000 miles common to diesel engines I would have been changing it OFTEN.  Freightliner said I could go up to 10,000 miles with that kind of service. 

I was just showing how much everyone has a different opinion on oil change interval-including FedEx!  I never changed the oil myself, as it would be hard to document properly, but I think it was at least 20 quarts in a 4 cylinder, turbo charged, and intercooled engine.  As you can  see, it was not a sprinter type.