oil add between changes

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453
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northeast
I am wondering, my 2006 lucerne 3.8L uses about 8 oz of oil per 1000. So a 4000 mile run would be 1 Qt. or a 2000 run would be 1/2 qt. etc... My question is should I add oil when down about a half qt? or should I just let it down to the lower fill mark and change at 4000 miles. thanks.. I am presently using kendall syn blend gt-1 5w-30, before that was shell dino 5w-30
 

PT1

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I have always topped off oil when it is down as much as 1/4 quart. But I check the oil & tire pressure in all my vehicles once a week. So, none ever have made it past 1/4 quart down. But I don't have any engines right now that consume any oil. I would top it off as soon as it is down below full at all.
 

lucerne06

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northeast
It has 16,000 miles on it.about 70 % city short trip driving. no indication of any leaks from anywhere..my last oil analysis was very good. Does it matter if you top off with the same oil and then get a oil analysis done? or does that skew the results?
 
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147
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Michigan
If you add make up oil and note it on the UOA they account for that. I have a 2005 Grand Prix with the same motor and use about .40 a quart every 3,500 miles or so. I am not going to top off until I reach the lower safe zone on the dipstick. Do you have 4 or 5 notches on your dipstick? Mine has 5. It seems that after 3000 miles or so usage has stabilized. 65K on the motor with 40/60 city/highway driving on M1EP 5w30.
 
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United We Stand
 Originally Posted By: lucerne06
It has 16,000 miles on it.about 70 % city short trip driving.
Low miles short trips more likely then not some of the usage is due to fuel contamination. I would also try a more shear stable 10w-30 to help with consumption. Normally I would add but with only 4k miles between changes I would hold off as long as the level is still safe on the dip stick.
 
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Lake Forest, CA
I would use 10W30 and add only if the level is below the min and still a long way to change. If the level is above the add line and close to time to change oil, then I would not add any.
 

lucerne06

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453
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northeast
It calls for 5w-30, how much of a difference (if any) good or bad , if I use 10w-30 instead? especially in the summertime?
 
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1,841
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United We Stand
No difference in performance during the summer but better NOACK so less consumption. Slightly thicker in the winter. Look at your UOA shearing some of which is possibly fuel related to short trips and low miles. You do appear to get the oil hot enough to burn most of the fuel off regularly.
 
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698
Location
Fontana, California
On fuel contamination: If there is fuel in the oil and the vehicle is driven on a long highway run at the end of the day, is the oil in the same condition before the extra addition of fuel? My guess is the oil will be in worse shape even if the existing fuel is burned off. I think about this with my beater aspire. I deliver pizzas in it. When it's busy it's a bunch of warm starts. When its slow, the car has to get back up to temps, which may or not be happening if the run is just a few miles. I do have a 30 mile jaunt with no traffic home every night. This car isnt worth a UOA hehe, just wondering because I have had to use other cars for this duty in the past.
 
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United We Stand
 Quote:
The evaporation loss is of particular importance in engine lubrication. Where high temperatures occur, portions of an oil can evaporate. Evaporation may contribute to oil consumption in an engine and can lead to a change in the properties of an oil. Many engine manufacturers specify a maximum allowable evaporation loss. Some engine manufacturers, when specifying a maximum allowable evaporation loss, quote this test method along with the specifications. Procedure C, using the Selby-Noack apparatus, also permits collection of the volatile oil vapors for determination of their physical and chemical properties. Elemental analysis of the collected volatiles may be helpful in identifying components such as phosphorous, which has been linked to premature degradation of the emission system catalyst.
Noack ASTM D-5800 Noack is a measure of the percentage of loss from vaporization of a given oil. A 10w30 has a lower precentage of loss when compared via Noack volatility test ASTM D-5800 to a 5w30. If your oil is seeing fuel contamination that will increase the oil volatility and when the fuel burns off it is taking some oil along with it. Switching to a lower volatility oil should lower consumption. With only 16k miles the engine may not be fully broken in yet as well. For summer time driving there is no risk what so ever.
 
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