Hi everyone, I have a 2000 Pontiac Grand Am with the 3400 V6 engine with about 270,000 km's (167,000 miles) on it currently. In 2018 I had some engine work done by my mechanic, I had both heads port polished with the oil valleys opened a bit wider for more oil flow, new head gasket, new valve cover gaskets and new upper and lower intake manifold gaskets.
At the time of the engine work I was using Mobil 1 advanced full synthetic 5w-30 oil, I did not really like this oil at all as it only lasted 5000 km's in my engine and it was smelling pretty bad when it got dirtier.
In the same year 2018, I then switched to the Castrol Edge synthetic oil 5w-30 (in the black bottle) and ran that oil up until 19,000 km's (11,806 miles), until it started to smell bad then I changed it after. In those 19,000 km's I only had to add 2.5 quarts of oil in my engine for the time being. I was absolutely amazed and astonished that I finally solved my engine burning issues as I didn't have to add too much oil in my engine.
In 2019 after using the Castrol edge in the black bottle I then switched to the Castrol edge extended performance 5w-30 (in the gold bottle). After a month of using this new oil I noticed that I had to add a quart once a month in my engine every time. Even though I had to add more oil I sticked with this new oil as it has titanium and it lowers the frequency of my engine's idle which no oil had ever done before.
In 2020 I used the same oil with the same burning issues but sticked with it anyways all the way though the year. I took more notice in my issues last year. I topped up my oil to the fill mark, whenever I would run my engine hard it would burn from the 4th hole to the 3rd hole on the dipstick.
I then changed my oil again after running that one up to 5000 km's thinking that I received a bad batch at the store.
I used the same oil in the gold bottle and only put about 1600 km's since my last oil change and had to put 700mL of oil in my engine.
I did notice that I had a slow leaking drain plug which may be contributing to my oil loss, and I also noticed a little bit of blue smoke upon start up but it goes away after a few seconds.
When my engine was taken apart I looked inside all of the cylinders and noticed that there's no cross-hatch on the cylinders anymore, which also maybe why I'm losing oil also.
Why would switching the oil sub brand make my engine lose the oil faster than the previous one? Would my engine being high mileage be the reason why I'm losing oil?
I also cannot go faster than 180 km's in 4th gear full throttle at 4000 rpm's on steep inclines. The speed gets stuck there and my car does not go any faster. Plus this is where mostly I lose oil from.
Any input or feedback will be greatly appreciated,
Thanks!
