You should be fine switching to synthetic, I have done so on several cars with over 100,000 miles with no problems (in one I even had lower oil consumption). The reason that you hear that you shouldn't switch on high mile cars comes from the original Mobil 1 back in the 80's when they didn't put a seal sweller in the oil. With older cars that had marginal seals the extra cleaning in the mobil would flush all the gunk out and they would leak like mad. Once mobile started to put the seal swell in, the problem went away.
I will throw in my opinion and suggest Mobil 1 synthetic, it is factory fill for porsche and mercedes. I have used it for years with no problems, and on a car that I had to pull the motor apart after 50,000 miles I found absolutely no sludge or other buildup, the motor looked brand new.
I've used Mobil 1 for my vehicles for years, I switched my FZJ80 to Mobil one 3000 miles after I bought it with 175k on the odometer. No more consumption than before, and no oil in my driveway. With only 92k, and the fact that it is a toyota, I would not even think twice about it and just start using synthetic.
On this topic of switching to synthetic motor oil:what weight is everyone using? ie:5w30/10w30/other?
the reason i ask is i was considering the switch to mobil 1 myself and one 80scool user stated that he was gonna use 15w50 for the summer in oregon,and that he used 10w30 in the winter,and he NEVER used 5w30...(this lister posted that walmart has mobil 1 gallon jugs for 18.88--not bad)
i wonder if a slightly higher weight oil,such as the 10w30 or even the 15w50 would help in a higher temp situation,such as when towing,would it help with overall engine temps etc....
it does not say on my invoice,but i am sure the toyota dealer used 5w30 for my last oil change,and as i am about a 1000 miles from my next change,but have a couple of hard tows on this oil,am gonna change it now and use the mobil 1 and i am not sure what weight to use(i know the manual states 5w30/10w30 as rec for my heat range(kinda overlaps),but as i posted in another thread,i am running it pretty hard for almost 2 hours straight and want to make sure its got what it needs.......
I wouldn't imagine down in WV any need to run anything other than the 10w30 year round. Up here in New England we can get cold enough to be outside the 10w30 range so I do use 5w/30 during the Fall/Winter months.
I'm using Mobil1 5W-30 (blue cap) year round for fuel conservation & better initial oil flow (comparing to 10W-30). However, if you're towing alot (or turbo charged), higher vicosity is recommended (Mobil1 15W-50 (red cap)).
I have always run the same viscocity as the recommended dino oil (10w30 mobil one for the LC).  on't know if it's the right thing to do, but have had no engine problems. Is there a compelling reason to switch for someone like me, I don't tow or haul heavy loads extended intervals, live in an area with relatively mild temps.
Or you can use what the big rigs use...M1 delvac 5w40 (packages says its recommended for heavy-duty use in extreme hot/cold temps). This stuff is pricey, though...$26/gallon at Petrol Lube truckstops. Somewhere I read that the current M1 supersyn uses a group III stock instead of a group IV (true synthetic like the old M1 trisyn)...can't confirm this, though. BMW factory fill is reportedly M1 delvac (rumored on BMW lists), as M1 supersyn isn't made in 5w40 and the viscosity/color is identical to that of delvac (so BMW owners say).
I started using M1 delvac on a 17-yr old 22re w/ 145K miles...so far, so good (ie, no leaks, consumption is the same as w/ dino). I chose it over M1 since diesel oils are supposed to have more detergents, acid neutralizing compounds, and have greater soot capacity than their gas-only counterparts. My hope is it cleans out any varnish in the engine. The other reason was the 5w40 rating since I live in the S. desert where it's over 100F in the summer, but winter nights are near 32F. I found a cheaper and hopefully just as good alternative with Shell Rotella T synthetic, also a diesel engine oil rated at 5w40 (the other brand sold at Petro Lube, but WalMart had 'em for $13/gallon so I got it there!)
The one thing I notice is that as the hotter weather comes in the oil pressure guage will read noticably lower with the 5w30 than after the switch back to 10w30. Which is expected with the lighter weight oil. 5w30 in S Cal. you might want to rethink that one, how hot does it get there in the summer?
5w30 is the recommended oil on my '01 honda (that's also what the dealer here uses). Since I was living near the ocean, max high was about 85F, min low around 47F. Typical highs/lows are 65/50F. Yeah, I know, one can easily run 10w30 year 'round in those conditions. 13K mi on dino 5w30 w/ oil/filter changes every 2K mi. Now I run only synthetic, will extend changing intervals to 4-5K mi w/ one filter change in between.
I heard the reason why most new engines recommend 5w30 is so the engine warms up faster (at the tradeoff of engine life) to reduce emissions.
Hey, Mobil and Shell claim their synthetics increase fuel economy by about 3%. This has been documented by trucking companies. So you can have your cake and eat it, too...problem is, this would increase engine life, and that's baaaddd for the Big Three.
What does Delvac say about use in hot weather? As I said in other post Rotella said for my high mi (200k mi) that 5w40 should be ok for upper midwest but not for AZ type weather. I didn't ask if it was becouse of my mi. I could use Rotella 15w30 dino oil in summer and 5w40 syn in winter.
My last comment wasn't at you personally just that the government has regulated the s*** out of the auto industry. Everyone blames the thirst for SUVs by consumers to have such a bad effect on our enviroment. But nobody realizes it was the government's regulations that ignited that thirst. By initially excluding trucks from the CAFE equation the only way manufacturers could offer the power concumers wanted was in a truck form. Which they did coupled with 4 wheel drive FOR SAFETY and away we went down the SUV trail. Now they decide to include trucks/SUVs into the equation and now with even high CAFE targets we have to sacrifice engine life for a better CAFE number. I find this s*** almost maddening.
I whatch how much my truck consumes per oil change to guage how much wear is in the engine. I suppose if that consumption stated to get high or if knocking sounds started I might consider a heavier oil but just to use it I don't think so.
thats what i figured but it was almost 90 here today and like i mentioned,when towing for almost 2 hours i wonder if i should have something a little heavier in there?
the 80scool lister stated that his wifes audi manual said that if it was over 100 degrees and you were going to run for MORE than 1 hour then you HAD to have something other than 5w30 in it.
my manual says from |-0-100->F use 10w30
from<-- (-20)-100-| use 5w30(preferred)
since it rarely gets below zero i will try a change with 10w30 mobil 1 and see how it works out
i used to run castrol 20w50 in most everything i had back in my younger(read poorer,worn out vehicles)days
ps:is it me or is the board a bit fussy today? i have to restart my browser after a couple of threads,and its not been this bad for a while(i had to restart my browser just to post this!!)
Is anyone in the group running 15-40 or something else other than 5-30 or 10-30? I'm not too pleased with what my O.P. gauge reads at a hot low idle, in gear, with 10-30. And no, I have not put a mechanical gauge on it to see what it really is.
I have always run 5W-30 in my truck since purchase (new). I've been running 5W-30 full synthetic since about 50K (at 91K now) and have noticed that the OP does dip to worrisome lows at idle. But I've also read (either BGB or OM) that this is "normal". Maybe it is, but I never really noticed these lows until I started using full synthetic. It may just be that when I switched is when I started to pay more attention. After having read this thread, I'm thinking of moving to 10W-30.
Kurt, I'll try to check the M1 delvac package tonight.It was designed for truckers who have to drive from hot places like TX/AZ to cold areas like Alaska. I only found this spec sheet (http://www.superiorpetroleum.com/html/delvac1_spec.html ).
If it helps, it won Lubricants World's 1998 product of the year. Couldn't search on their webpage, though.