ive read that you should re-torque the valve cover bolts every oil change. and my truck had 186K when i bought it. the PO always used mobil clean 5000. i switched right over to synthetic and ive had no oil leaks, so i kinda doubt its the syn change that caused it

 

the lucas stuff isnt really made for that either...it does help but your best bet is valvoline high mileage dino oil..(or blend) it has an additive that causes rubber to swell and also has a similiar effect on gaskets I believe... If you have poorly sealed gaskets the synthetic will find them and leak it flows better and acts like a thinner fluid in that sense... I had the same issues in my vw...its hit or miss.

 

^VW's always leak oil though....

 

when i did my timing chain and water pump, i got it all tore apart ,timing chain cover off and noticed my balancer was seperating and walked back into the the cover where the timing mark indicater protruded out on the cover and it walked back and seperated far enough to rub a hole right thru the cover at that timing mark spot,thats where my oil leak was coming from .i just thought it was the front seal on the cover... i had to get a new cover at the junk yard,and bought new balancer. probally not your prob but it would be a good idea to check the balancer once in awhile i had no clue this had happened, dont know if this was a common prob for the balancer to do this....

 

well it was 100 times worse with the synthetic. literally overnight I developed leaks in 5 places after going to a lighter weight synthetic.I went back to 10w30 dino and most of the leaking stopped or slowed considerably...I had a pool on the cardboard every day! now I just have one small leak to fixafter replacing gaskets...

 

Seems like the leak has slowed down now, But I can smell oil burning when I turn one heater and A/c, or when I pop the hood, its STRONG! So its leaking out somewhere and getting on the exhaust or somthing hot enough to make it burn.

 

I use Supertech 10w30 full synthetic,been using it for 300,000 miles. Got tired of paying for those names.It stays clean in between 5-6000 mile changes.I put one of those teflon additives in it at 75,000(slick50 I think)Got over 446,000 on it now.No oil leaks on the driveway.Never had the valve covers or oil pan off of it.

 

how much RTV did you use in the corners of your intake when you did the plenum?

 

Plenum has never been off either.

 

sounds like bad intake gaskets changeing the rear main seal might make things worse just because of the add oil pressure i know thats wht happin with mine when the intake gaskets went out.but if you have the time and mouney. just do your rear main the timeing cover and valve covers. if still leaks then intake gaskets