Synthetic VS. Regular oil reliability

[Yaris Hilton]

I'm betting on the "regular" oil and 5000 mile changes. If it were necessary to use synthetic oil to avoid costly repairs down the road, don't you think Toyota would've recommended it?

FWIW, over the years I've run a number of cars well above 100,000 miles without problems on conventional oils, and the only 2 engines that have suffered any lubrication related failures (a bad timing chain and excessive oil consumption) were run on Mobil 1 with an extended drain interval then promoted by Mobil.

Also FWIW, I had the top end off of my old 1985 Harley that had only used Harley-Davidson branded oil and Castrol GTX after 60,000 miles. The pistons, rings and cylinder bores were all in perfect shape, measured within new stock specs, and had no visible scratches. The original honing marks in the bores all looked fresh. I put it all back together as it was (replacing the defective base gaskets as well as installing some performance parts like a cam, carb, ignition module and exhaust.) No synthetic oil could've performed any better there. That was an air cooled engine that ran a lot hotter than a Yaris engine does. Conventional oils have advanced a lot since then, too.

IMO the synthetics mainly have advantages on the extremes of operating temperature, and if you're not pushing the limits there, with regular changing the "conventional" oils will do as well. I use the quotation marks because the "conventional" oils haven't been based on petroleum distillates for a long time. With processes like hydrocracking used so extensively, it's arguable that they're "synthetic," though not built up as polymers from small simple molecules, and many of the ingredients of older mineral oil bases that were bad formers of sludge and varnish can no longer be found in them.

There are many enthusiastic advocates and users of synthetic oils on this board. Many of them use extended drain intervals, which make the increased initial cost of the synthetic less daunting. Unless they're regularly using an oil analysis service to tell when it's time to change it, I fear some will come to grief as I did. "Conventional" oils as well as synthetics could run safely well past recommended change intervals under ideal engine operating conditions, but most drivers operate most of the time under what car makers used to call "severe" operating conditions that cause more oil contamination. I am unconvinced that synthetics can safely run longer with this.

Modern engine control systems and reformulated, low-sulfur fuels have greatly reduced oil contamination for all of us, though. You ought to see pictures from an old textbook I have from the early '50s on engine lubrication showing the deposits on engine parts test run with the best quality fuels of the day and low grade stuff containing lots of gum forming components! Fuels are far less variable today than they were, but are still an important part of the overall picture.

Most people working on cars today have probably never seen an engine with the heavy black brittle "carbon" crusts, thick tarry sludge deposits, and slimy, mucky, gray-black pudding-like glop that were standard findings in engines of the past. It's amazing that they could run as well as they did. We've come a long way!

[127.0.0.1]

Originally Posted by Yaris Hilton

I'm betting on the "regular" oil and 5000 mile changes. If it were necessary to use synthetic oil to avoid costly repairs down the road, don't you think Toyota would've recommended it?

FWIW, over the years I've run a number of cars well above 100,000 miles without problems on conventional oils, and the only 2 engines that have suffered any lubrication related failures (a bad timing chain and excessive oil consumption) were run on Mobil 1 with an extended drain interval then promoted by Mobil.

Also FWIW, I had the top end off of my old 1985 Harley that had only used Harley-Davidson branded oil and Castrol GTX after 60,000 miles. The pistons, rings and cylinder bores were all in perfect shape, measured within new stock specs, and had no visible scratches. The original honing marks in the bores all looked fresh. I put it all back together as it was (replacing the defective base gaskets as well as installing some performance parts like a cam, carb, ignition module and exhaust.) No synthetic oil could've performed any better there. That was an air cooled engine that ran a lot hotter than a Yaris engine does. Conventional oils have advanced a lot since then, too.

IMO the synthetics mainly have advantages on the extremes of operating temperature, and if you're not pushing the limits there, with regular changing the "conventional" oils will do as well. I use the quotation marks because the "conventional" oils haven't been based on petroleum distillates for a long time. With processes like hydrocracking used so extensively, it's arguable that they're "synthetic," though not built up as polymers from small simple molecules, and many of the ingredients of older mineral oil bases that were bad formers of sludge and varnish can no longer be found in them.

There are many enthusiastic advocates and users of synthetic oils on this board. Many of them use extended drain intervals, which make the increased initial cost of the synthetic less daunting. Unless they're regularly using an oil analysis service to tell when it's time to change it, I fear some will come to grief as I did. "Conventional" oils as well as synthetics could run safely well past recommended change intervals under ideal engine operating conditions, but most drivers operate most of the time under what car makers used to call "severe" operating conditions that cause more oil contamination. I am unconvinced that synthetics can safely run longer with this.

Modern engine control systems and reformulated, low-sulfur fuels have greatly reduced oil contamination for all of us, though. You ought to see pictures from an old textbook I have from the early '50s on engine lubrication showing the deposits on engine parts test run with the best quality fuels of the day and low grade stuff containing lots of gum forming components! Fuels are far less variable today than they were, but are still an important part of the overall picture.

Most people working on cars today have probably never seen an engine with the heavy black brittle "carbon" crusts, thick tarry sludge deposits, and slimy, mucky, gray-black pudding-like glop that were standard findings in engines of the past. It's amazing that they could run as well as they did. We've come a long way!

194,000 on my 4runner, got it in dec 1998, always ran mobil 1 and changed at 10,000 miles, thing is rock solid, gets better than epa, doesn't lose more than 1% of the oil over 10,000 miles (in other words, very tight motor and good seals and rings)

[scape]

Originally Posted by Yaris Hilton

IMO the synthetics mainly have advantages on the extremes of operating temperature, and if you're not pushing the limits there, with regular changing the "conventional" oils will do as well.

i think this is one of the reasons it is desired, that and extended intervals to drain-- but i also think people run synthetics at longer than recommended for the oil filter and most people don't realize that. the filter has a life of it's own and no matter what oil you are using, the filter is very important to filter out many, many things; so maybe the oil itself did not breakdown, but there are things to be filtered nonetheless. http://yarisworld.com/forums/showthr...ghlight=filter

I myself stick to regular oil changes at around 4500 - 5000 miles.