I'm using a 1981 Ford 302 V8 w/ 96000 original miles as the test bed. It uses the standard Motorcraft 2150 2-bbl carb (no electronic stuff). It was originally fed 10W-40 dino every 3 months w/ a new filter for the past 20-21 years. I tried using 10W-30 and 5W-30 at one point, but for some reason it affect start up. The oil seemed to soak the spark plugs and all the cranking would flood the engine. Fast forward a few months (using 10W-40), I changed the old decrepid valve stem seals with new FelPro Polyacrylate(sp?) valve stem seals. Now it starts up with 10W-30 and 5W-30 without any problems. After a few months on 10W-30 and 5W-30, I switch to Synthetic 10W-30 but I accidentally flooded the engine once w/ a disconnected evap hose. I found that switching synthetic oils would become too costly with this carb'd motor - so I got an idea. I would use 1 quart Super-Tech synth with 4 quarts of Pennzoil dino (only dino I have). I figure the moly in the dino would help, and the synthetic (group 3 albeit) would do its part. Now fast forward to sub zero (F) temperatures in NJ. It starts, runs, and drives like it used 5 qt of Synthetic 10W-30. I don't hear or feel any difference with this setup. I was wondering - if I continued to do this even on modern engines like a brand new Ford 5.4L SOHC V8 or a slightly used 4.6L SOHC V8 for the next 5-10 years - what would happen? Would it sludge up faster than if I used straight dino or straight synthetic? With the failing economy, I don't have a lot of $$ to spend on Mobil 1 engine oil. If I can get by with my "ghetto" synth blend routine, I think it'd be worth it. With 5 qt of supertech dino (has moly) w/ 1 qt synth, it comes to roughly $1.20 a qt for synth "blend" Any thoughts on this? If I overlooked something simple - please shoot this down gently That's all I ask! Thanks in advance!