Celica Forums General Discussion General Engine codes and Synthetic Oil

I have a few questions...

1. I'm going to start changing my own oil and I want to switch to synthetic. Thing is, my car has almost 99,000 miles on it. Should I be concerned about oil leaks?

2. I got a CEL yesterday and the code is P0420 - Catalyst System Efficiency Below Threshold. The three possible causes for this are Gas leak on the exhaust system, heated oxygen sensor, or catalytic converter. I thought someone on here got this code and it was the cat but I'm not sure. I think it is the cat, and, if it is, I want to replace it myself. How hard is it to replace the cat? Also, If I can replace it myself what kind should I get (what inlet and outlet)?


Thanks

if it's the cat (which it probably is) toyota has to replace it. laws state that catalytic converters have to last a minimum of 100,000 miles (it might even be 200,000 miles). however, thats IF you have no aftermarket modifications whatsoever.

as far as synthetic..100k miles isn't that much. synthetic oil shouldnt be a problem. check wear you park and use the dip-stick check every week for about a month to see if you're losing more than normal amounts of oil. keep in mind that driving hard will burn up more oil faster.

I do have mods, is it hard to replace the cat myself?

not if you know how to weld...which it probably will require unless you want to use flanges...you'd have to get someone (or yourself) to weld those on as well though.

everything comes unbolted relatively easy once you get access to the back of the exhaust manifold. i found that using wd40 or liquid wrench works really well when trying to get the hangers off the rubber holders for the rest of the exhaust. then it's just cutting & welding the new cat in.

what size inlet/outlet (I'd guess 2.25 in and out) any recomendations on brand (I was thinking about getting a Magnaflow high-flow stainless steel cat)

I have 62k and i just switched to synthetic oil...and maybe this is normal...maybe it isn't..but i swear my engine is sweeter during startup and driving...i can definitely tell a difference...whether it's just in my head or not.

The thing is...i let the old oil drain for like 30 mins to get as much out as possible...and i put almost 4.5 quarts in...i'm sure about 4.4 quarts like you're supposed to for the GTS...and i've been checking and no oil is leaking from the drain plug or the filter...but my oil is low. When i pull out the dipstick it shows at the first dot...shouldn't it be up to the second one? Since the synthetic oil is smoother etc...do you think it just runs off easier and therefore shows lower on the dipstick by the time i pull it out?

No, checking the oil with synthetic is the same as normal oil. Just be sure to get the oil level correct, then wait a couple of weeks and check again to see if its using oil. It might also look a little low just because you let it drain for so much extra time too.

ttt

i forget the exact size of the piping. that cat should work just fine though. you can always measure the piping size yourself if your not sure..jack your car up and take the diameter of the piping by using two levels (top & bottom) theres also another tool that makes it easier but i can't remember the name of it for the life of me. its basically almost like an L-shaped tool with a another movable straitedge so you can get the diameter equally. the whole product looks like an "F" with the lower part being movable...lol i know its confusing...i just can't remember the name of it.

ditto. synthetic oil does flow more easily..but not enough to NOT show on the dipstick. make sure your car is parked on flat ground and fill it up slowly until the dipstick shows near the top dot or at least halfway.

thanks for the help Caleb

no prob bro, i'm hardly an expert though check around and see if you can find out some more info.

personally, i'd go to a muffler shop and talk to one of the mechanics there to see what they would do if they were doing the project. the more info the better..even if it's repetitive.

i run synthetic, castrol syntec, i have 55k, but really, 99k isn't high, i would try the synthetic, and if it leaks, you know, just check the oil very often to make sure.

ok, now I'm confused, I went out to my car this morning to go to class and turn the car on. Guess what, the cel went away.

Is the ecu just not picking up the problem right now

Oh, and the synthetic is working just fine so far, seems to be operating a little smoother too.