Hello forum. I figured this would be the place to ask. I have a '98 740il with 235k miles on it, driven in FL, sees a good mix of highway and around town. I drive it pretty easy, but get on it at times. The V8s in these older BMWs run hot -- 100-110*C. Does city driving during the week and 500 mile round trip highway road trips on occasional weekends. Been in the family since 29k miles. I maintain everything myself. For years the well known euro shop in south FL used Castrol 20w-50 in it, so I continued with that when I got the car 8 years ago. I dropped down to 10w-40, when I spent time in CT in school, then switched back to 20w-50 when I moved back to FL. Reason for asking this is that I noticed with the my higher mileage that I "burn" about a quart every 3-4k miles. I just had to top up a quart to get back to full the other day after about 3500 miles. I change the oil every 7500 miles or so, which is half of the normal interval that the car says to do with the "oil lights" in the dash. I buy my oil at Walmart because they've got the best price. They were out of the conventional 20w-50 the other day so I start looking around and thinking about all the other oils there. I see Castrol High Mileage, Castrol Magnatec (blend), Castrol Edge (synthetic), Castrol Edge High Mileage, and I start thinking...should I at least be using a high mileage oil? My wife has a 540i (same engine as 740) that we got with low miles, and I started with Mobil 1 Full Synthetic European Formula in that car (0w-40 I believe). And that's all I've used in that. So just looking for advice. I'm leaning toward staying with Castrol in my car (for whatever reason), and maybe a high mileage oil? I thought I read somewhere it is not good to switch between dino oil and synthetic, but that was years ago. Can I (should I) go to a full synthetic? Thanks!