You may not have a visible oil leak, but it may be "using/burning" oil out the tail pipe. Take a look at your exhaust pipe, is it black a sooty?
You may be experiencing "blow-by" which is a term in relation to oil passing by the piston rings. 10w30 would not solve this problem. If you have not yet had a dye test in your oil, I also recommend this procedure, which is fairly inexpensive...a black light dye is injected into the system where you run for about 50 miles of circulation where if there is an external leak it can be detected by a black light.
That is a great question. It is possible they can not find a leak because there is no leak. Sometimes as the engine ages, oil tends to build up inside the engine and cause the oil to burn. In extreme cases, you would see some smoke coming out the back. By using heavier weight oil, you are masking the problem. Maybe a better solution would be to fix the cause of the problem. When was the last time you had a tune-up? The pcv valve allows the oil at the top of the engine to breathe. If the valve is clogged, it will also cause oil build up.
〉 Answered on Nov 20th, 2010 by Audra Fordin, Owner at Great Bear Auto Shop
Cars normally burn a quart of oil between oil changes. Changing to 10w30 could help.
〉 Answered on Oct 20th, 2010 by Barb Petrey, President - DBK Enterprises Inc at Jiffy Lube
Hello Maria*If your vehicle has over 50,000 miles I would use 10w 30 during colder months and 10w 40 in the summer. If the engine is not leaking oil*the only other cause for oil loss is that the engine is burning it*indicative of piston ring or valve guide/seal issues. Hope this helps; thanks Super Girls Auto.
〉 Answered on Oct 20th, 2010 by Laurie Sarno, Co-Owner at Super Girls Auto
You should use the oil that the manufacturer recommends. It*s possible that you*re just burning the oil. If you have high mileage, meaning over 100,000, this is not unusual. My 88 Toyota burns about a quart between oil changes and has 295,000 miles.
If you don*t have high mileage then you should have your engine checked. It could be the oil is getting past the rings or the valves.
〉 Answered on Oct 20th, 2010 by Lori Johnson, Owner and Instructor at Ladies Start Your Engines