2006 Gen2: Oil Consumption Almost Completely Reduced

I bought a 2006 Gen2 with about 200k and a bad battery. After getting the battery replaced and driving my Gen2, I found that the motor was consuming about 1/2 quart of oil every 1500 to 1700 miles. Not a terrible situation but not ideal.

As a result, I did the following: i.) changed oil change interval to 3500 to 4000 miles; ii.) started using Shell Rotella straight 40W oil*; iii.) installed an oil catch can between PCV valve and intake's vacuum port; iv.) drive my Gen2 almost every day; and v.) use only 3.5 quarts of oil at each oil change rather than the maximum of 3.9 quarts (appears to reduce windage issues).

Oil consumption has been getting better and better (less and less oil consumed) since I bought it. Oil catch can is now catching about a TBSP of spoils every 1800 miles (versus 6 ounces every 1800 miles when I first installed it). Oil catch cans usually usually capture more spoils in winter (so we shall see how much spoils I am capturing this winter).

I am about 2200 miles into my most recent oil change and the oil consumption is between 1/10 quart and nil. I need to wait until the next oil change (in about 1800 miles) to determine the absolute consumption during this oil change interval. During this oil change interval, I drove about 400 miles with my 5'x8' trailer attached (IOW not easy driving for the engine).

My theory: oil rings were gummed-up when I first purchased my Gen2. Rings were ungummed by reduction in blowby (reduced by using straight 40W oil), reduction in windage by shortsticking oil level at each oil change (namely, using 3.5 quarts), reduction in spoils in crankcase due to oil catch can, daily driving, and Shell's anti-sludge and varnish additives. It all seems too good to be true but it really is happening here.

*- Shell Rotella straight weight oil has "optimized dispersant content to help prevent engine sludge and varnish deposits." See Shell Rotella® T1 Straight Grade | Shell ROTELLA®

PS I have never had an oil burner stop burning oil before. But my mechanic friend says he has seen it happen every once in a while in his 50+ years of wrenching.

PPS Since installing the oil catch can, the P0420 DTC no longer comes on except for one occasion where I failed to empty the oil catch can on a timely basis (thereby allowing spoils to be sucked into intake and ultimately end up in the exhaust, cat and sensors).

 

My Gen2 is placed on a lift when oil is changed. Additionally, I make sure that the plug is open for at least 5 minutes to get all the oil out.

A second check on full emptying of crankcase: I make sure that the container of new oil has only 3.5 quarts of oil in it at oil change time. Then, I check the dipstick after refilling with oil and briefly running. Refilling with 4/10 of quart less than maximum places oil level between max and add-oil dots on the dipstick (which is exactly what happens).

 

I will likely be using Shell Rotella 10W-40 or 15W-40 this winter coming up.

 

Initially, when I purchased my Gen2 Prius, I had a ton of blowby. After I tired of constantly topping off the oil and P0420 codes, the blowby was captured by the after-market oil catch can that I installed. The spoils collected in winter typically were made up of the following: water (20%), unburned fuel (5%), aerated oil and water mixed into an emulsion with the color of peanut butter(50%) and consistency of a loose mayonaise, and motor oil (25%). Initially (in winter), I was collecting about 6 ounces of spoils every 1500 to 1800 miles. Today (in summer), I am collecting about 1 TBSP of oil only every 1800 to 2000 miles.

Straight 40W restored compression to my 1.5l motor and greatly reduced blowby. In addition, Shell Rotella has anti-varnish and anti-sludge additives which apparently removed the varnish and sludge from my rings over about 12k miles (or three oil changes). Thereby, resolving the oil consumption problem (with varnish and sludge removed from the rings, my oil consumption is now almost nil).

 

Hot and cold cycles of a gasoline engine cause water condensation (larger temperature difference in winter thus more condensation in winter). Water that I was finding in my oil catch can in winter was of two ("2") types: i.) plain-old-water from condensation; and ii.) plain-old-water mixed with aerated engine oil* (thereby forming an emulsion with the color of peanut butter and consistency of a loose mayonnaise). Frequently, automotive engine oil is aerated by windage (usually, crankshaft weights striking oil in crankcase and aerating it). IOW, no coolant is being consumed, water is condensing inside the engine (and being trapped in my oil catch can), and some of the water condensate mixes/emulsifies with aerated oil to form the emulsion with the color of peanut butter and consistency of a loose mayonnaise.

You can find pics of spoils from my catch can at post #11 in the following thread: Oil Catch Can from Ebay Installed | PriusChat

*- emulsions are an exception to "oil and water do not mix". Similarly, mayonnaise is an emulsion formed by mixing aerated egg yolk (water base) with oil.

PS Almost no spoils now (summer) being collected in the oil catch can. Additionally, almost no oil consumption any longer.

 

12292021 Update:

Oil consumption continues to be minimal. I recently returned from a 2500 mile trip where I was traveling at 70mph to 74mph for hours and hours. Normally I operate my Gen2 at 61mph or 62mph. Despite increased travel speed, oil consumption was very small (maybe 2 or 3 ounces). I am still running Shell Rotella 15W40. I have put about 64k miles on car in the last 26 months. And, oil consumption continues to be minimal despite having 264k on engine and transmission.

 

Almost time for next LOF. I am contemplating switching from Rotella 15W40 to Walmart's Super Tech 100% synthetic oil 10W40. I change oil and filter about every 5000 miles. As far as I can tell, the detergent in the Shell Rotella over the last 60k of miles in combination with the oil catch can have removed the engine sludge and unstuck (the previously stuck) piston oil control rings. Please let me know your thoughts, recommendations and concerns on switching from Shell Rotella synthetic 15W40 to Walmart 100% synthetic Super Tech 10W40.

 

Oil catch can is capturing about 80% of catch can volume every 2000 to 2500 miles (BUT ONLY IN WINTER TIME). Over time, the composition of oil catch can has changed. Namely, less oil, less oil/water emulsion, more water and a bit more raw fuel.

 

What is "SAPS" content?

 

I went to three different stores (namely, Walmart, Tractor Supply and Lowes) multiple times. All are sold out.
Or, in the case of Lowes, it appears they no longer carry Shell Rotella in their stores.