I switched over from the dino oil to full synthetic (Royal Purple) a few months ago, back in about Feb or so. I'd just bought the car in December, and the PO had done maintenance on it a week prior, so I didn't see the need to replace the fluids. Now, because I drive so much, I can't afford to change the oil too often. I do it about every three months, or 6,000 km. Last time I changed it was sometime in May, so I'm due for another change.
Now, yesterday I was doing a fair bit of driving. I'd done about 100+ km during the day, and as I was driving along a street with a slight incline, the car started bogging. It had been running worse for a couple days, but it had started raining about the same time so I thought perhaps it was just moisture content in the air. I would press on the gas pedal, and the engine wouldn't increase revs for a second, and then it would kick in and start accelarating. Also, the engine was running a bit hard, as if it lacked power. So, yesterday as I was driving up the hill, the engine started bogging again, only this time it would take a second for the engine to kick in and start accelerating, and then it would bog again, for a second, and repeat until I got to about 10 or 20 km/h, then it began to pick up again. At the top of the hill I turned the corner and drove another two blocks, when I noticed my revs at idle were way too low... about 500 rpm. It was still weak and chugging along, so I pulled over to the side and put it into neutral. It smelt a little like oil burning or something inside, so I shut off the engine and checked all the fluids. None of them were low, and the oil had no debris or anything and was clear enough. I restarted the engine and gunned it up to 5,000 rpm a couple times, when my cousin and sister (who had gotten out of the car) noticed black smoke coming from the exhaust... When I looked out the window, I could see it too. I revved it a few more times to see if it was burning oil, or if there was something just stuck in the pipes. The black smoke kept coming out under hard revving, but there was nothing there during idle, which had returned back to its spot at about 1,000 rpm. I looked at the ground next to the exhaust, and there was a black stain on the curb and grass... it looked like there were bits of soot collecting around the bottom of the curb. The truck was running better though, and I had to get it home one way or another, so we got back in and drove home.
Now, the truck seems to drive better, and there's no more black smoke, save for a tiny bit when dropping the revs in neutral after revving it hard. Also, I don't want to jump to conclusions, but it seems as if the potential valve tick I may have had before is gone. I did want to ask... does anyone think it's likely that the synthetic (I run Chevron gas as well, not sure if it makes a difference...) has finally cleaned out years worth of crap built up in the engine, or am I burning oil or something else equally bad?
Fil