I got great advice a month or so ago asking about a syn oil for our high mileage ES300, so now I'm back re: a slightly more problematic SUV vehicle in our stable. The Patient: I have a 1998 Acura SLX (rebadged Isuzu Trooper), 159k miles, excellent condition. The vehicle has a known issue with inadequately designed oil control ring drain holes, which tend to clog and increase oil consumption. This affected the 3.5l V6 models from 1998 to the early '00 model years until the rings were re-designed. I believe it is the same issue that plagues the 2006-2011 2az-fe I4 Toyota engines. I have followed Isuzu forum advice with maintenance work-arounds and I've got my oil consumption tamed. I'm desperately not interested in tearing down and replacing rings. History: I've had the vehicle 4 years/20k miles (not a daily driver, clearly). When I got it, it burned oil lavishly. The last 9k miles, on the recommendation of Isuzu experts, I've used Mobil Delvac 1300 HD diesel oil. 10 months ago I treated the rings w/SeaFoam while it was off the road for a big service (That consisted of squirting each cylinder via the plug hole with an ounce or so, letting it sit for a week before blowing out and re-starting). I now have oil consumption to little/none (= or < .5qt/4k miles). I think the HD oil was helping gradually, but the ring soak made the big difference suddenly, clearing the too-few passages and generally cleaning the rings. Though it goes few miles a year, it is also now going generally 20 miles or more each way when it is driven instead of a few short hops. I believe that is helping, too. I'm 4k since the last oil change (10 months ago). So now I'm re-considering the oil to use now that it's not burning. My mileage has dropped dramatically with the 15w-40 HDEO, and that's my only concern vs. staying with the Delvac 1300 or similar. Weather/climate is western WA/Seattle, so pretty mild. Generally 40F to 80F year-round. A picture below to demonstrate that once a year, that is exceeded. My thoughts are: 1) Is there a 5w-30 passenger oil that can give me the cleaning power of the HDEO? 2) Or a different HDEO like a Rotella flavor with a more mpg friendly weight? 3) One of these in a syn or syn blend that makes sense to use now that it is not consuming oil? 4) Stick w/15w-40 HDEO? I understand from reading elsewhere that the loss of efficiency/higher temps of the 15w-40 is also beneficial in helping it keep the rings clean, so I'm unsure of the trade-off vs other oils/weights/detergent effect. On my shelf I look and I have 2.5 gallons of 15w-40 mineral HDEO, and a full sealed 5qt. of 5w-30 Pennzoil Platinum. Would mixing those in some ratio give me any benefit or be a bad idea (I hear people say they do that, but I'm no oil expert so I have no idea if it's good or bad and why I am asking questions here and not winging it on my own. ). Looking forward to the typically good and educational advice here.