Geo - Metro :: 1994 - Massive Oil Burning Under Load But Barely Any At Slow Speeds

I recently got my hands on a 1994 Geo Metro 1.0L 3 cylinder. Actually I got TWO of them. One had a bad engine (burned valves) but was otherwise a good car while the other was junk (expect for the engine) and I am amazed the suspension didn't separate from the body due to the rust. So, I decided to swap the engine from the junk car to the good car. I replaced all seals and gaskets external to the engine plus the PCV valve and gave everything else a good cleaning. The only seals and gaskets not replaced were the intake gasket, head gasket, and exhaust gasket as the engine was swapped in a complete manner. I also did the timing belt and water pump while I was in that far as well as did the plugs/wires/cap/rotor when putting it back in. I also ran an oil change through of cheap oil and some Seafoam and Marvel Mystery Oil to clean out any sludge as it looks like oil hadn't been changed real well in this engine. This oil came out pretty dirty after like 30 minutes of idling.

This little car runs amazing overall and keeps up with traffic and is way more peppy than I would ever imagine! It is also getting somewhere between 50-55 MPG and is fun to drive kinda like a big go kart. There is ONE MAJOR issue! If I get on a highway and try to maintain speeds of 65MPH or faster on big hills, I am guaranteed to get massive smoke clouds from the valve cover area filling with oil and puking it through the PCV/breather assembly right into the intake. I tried more oil changes with synthetic oil and this kept happening. I also ran Seafoam and MMO through the oil and drove it like 30 miles before the change. The oil came out really black each time. I can now actually see bare metal on the inside of the valve cover area through the oil fill where before it was all black after all these oil changes. I also replaced the PCV once again for good measure as it was like a $6 part.

I drove about 100 miles on the highway and started getting massive smoke screens every time I got a long uphill grade and tried to maintain speed, especially if I stayed in 5th gear. The car had more than enough power to make it up the hill in 5th but would smoke under the load. This began to make me suspect I had a serious blowby problem. I had a quart of oil in the car and added all of this during a couple stops on the way. I was at or slightly below the low mark when I decided to head home so I found a parts store and purchased a quart of the cheapest store brand 10W40 oil I could find and used this to get home. It still smokes quite a bit but maybe not like on the way there. I also had the wind at my back so I figured part of this was load dependent.

I was at or just below the fill mark on the dipstick when I got home so I added some more 10W40 oil I had sitting around for an ATV I no longer own. I know this is formulated for motorcycles and ATVs but figured I wouldn't hurt the engine any more. I also added some auto trans fluid as I know some people say the detergents in this can free stuck rings and work wonders in a neglected engine. Again, how can I do more damage to this engine than has already been done? The car calls for 5W30.

I have pretty much resigned myself to the fact that this little engine had 170K of not the best maintenance and is due for a rebuild. My plans are to keep driving the car while rebuilding the other engine with bad valves. I am glad I kept the old engine around. The car seems to be doing a lot better on the mix of thicker oil and ATF but wonder how long it can go like this. I took it out on the highway and really pushed it hard to see if I could make it blow smoke and it would not. It MAY have consumed some oil on the dipstick but I am even not sure about this. I am not adding any until I can see a definite drop in the level.

Here is my next question. What is likely the solution I found? Thicker oil sealing worn rings better? ATF dissolving crud around stuck rings? When/if I change the oil before I get to the rebuild, what weight should I use? 5W40 maybe? Also, these engines are notorious for burning valves if a thicker oil is used as the hydraulic lifters don't allow them to close completely.