quote:
Originally posted by monarch:
The '98 to '02 Corolla engines are all the same and none had any sludge problems.
The PVC system has always been highly
efficient on Corolla engines according to a Toyota technician and he feels that's the reason Corollas are immune to sludge.
Well almost immune - the technician says
owners who run dino oils for 10,000 - 15,000 miles or Amsoil synthetic for 25,000 miles WILL get sludge - sludge thick enough to hold a knife stuck in the bottom of the oil pan.
PCV didn't have anything directly to due with the sludging of the toyota engines. The reasons are a multiplication of little things that makes a difference and why earlier models vers newer models sludged.
The main reason toyota engines will tear an oil up is because they are the only one that use gears to drive their ohc's where everyone else uses either a chain or belt. The chain has very little area that oil is exposed to thus not shearing the oil and the belt is not submerged in the oil. The gear system used by toyota is uniqe and the motor is one of the best on the market.
Here is a picture of a 12,000 mile toyota sludged engine(yes it was new). This was taken after they had attempted to clean it with a brand new win's engine flush machine for 45 min's.
Notice the two gears,like in a motorcylce engine that shares the transmission oil, This is where oil is squeezed and tends to wear down the VI's in standard conventional oils, causing the oil to drop in viscosity at approx 3-4,000 miles of use depending on the quality of the oil. Once the oil thinned down due to the vi's breaking down, then the broke down vi's would now become a contaminent and due to the lighter viscosity, the oil couldn't cool as well so the engine would begin running hotter which would heat the oil and cause the oil to cook which would tend to burn off and increase in viscosity or thicken.
In all the engines that had been sent through repair at this toyota dealership, not one pcv system was contaminated nor was one ever replaced or cleaned. All were reinstalled on the new/rebuilt engine.
Now, why all of a sudden around 97 did all this start happening? Because in 96 the oil industry changed their formulation from SH to SJ, lowering the antiwear additives's and also many changed from group I to group II base stock around this time which actually was a drop in base oil quality from the group one.(notice that m/c recommends SH rated motor oil but not any newer than that due to the antiwear additive levels) Add that on top of toyota trying to extend drain intervals from 3k to 5/7500 and many newer cars also started to pack the engines in tighter places putting more demand on the oil due to less air flow across the engine. Now let me point out at this time that anyone that changed their oil at 3k intervals, had no evidence of sludge whatsoever. The only sludged engines where ones that tried to follow the extended drain intervals.
Now due to all of this, using a good synth based oil such as m1,amsoil, and even schaeffers synth blend, You could and can extend your oil drains out. BUT, I advise anyone doing this go no farther than 5k drains then do an oil analysis to see how the condition of the oil is holding up. From that information, increase the drain intervals to the 7500, at that point, if the analysis shows good, then you'll be alright. What many do not realize,(this is why amsoil and many other companies don't give recommendations), is that due to all the different types of driving conditions that exists, there is no way to determine if you're safe at the extended drain with out taking the time to establish this with oil analysis. The cost of this is very reasonable and for the investment of an $20-$40,000 piece of equipment, you'd think this is not a big investment for the insurance of engine reliability on that investment.