HI ART! My commuter car has recommended 7500 mi. service intervals. Guys who actually run those intervals have all had to replace the oil filter/separator/breather assembly because a rubber diaphram ruptures and pressurizes the crankcase which tends to blow out things like frt & rear main seals, camshaft seals... makes a BIG mess when that happenes.
I try to do 5000 mi service intervals but sometimes get up to 5500, last one was almost 5700 mi. And I've NEVER had that rupture problem. Volvo even extended the warranty on that problem from 5 yrs 50,000 mi to 120,000 miles with no time limit. Some guys have had the problem 2-3 times.
Some auto MFG's have started recommending shorter service intervals now days. People tend to stretch them to the limit and then some, and warranty repairs increase costs to the MFG. I know Toyota & VW have done this.
Your co-worker's Neon sounds like my first car. Was only 3 yrs old when I got it, odometer showed 30,000 miles but speedo didn't work. Probably had more like 130,000 miles. The little 307 V8 was using about a quart of oil every 200-250 miles, then I ran a quart of Rislone thru it. Yes, it loosened up the rings, also destroyed what was left of the valve stem seals and ended up using a quart every 125-150 miles. I carried a case of 24 quart cans... yes, METAL cans, not just the top & bottom lids, in the trunk and added a quart of oil every $5-$7 worth of gas. Every six months or so I'd spin on a new oil filter and add another quart of oil. So yes, No oil changes needed there! It was burning the oil too, no leaks!
I talked to several different good mechanics and finally found one in my little home town of 100 people who said he could fix it. The Small Block Chevies just used a simple o-ring around the valve stem as a seal, and it could float up & down. My valve guides were loose, the mechanic said replacing the o-rings would problaby slow down the oil burning for a short while then start burning again. He was right. I drove over 650 miles without adding oil, then had to start adding again, ended up around 150 mi/quart.
On the other extreme, there's SON's truck, an '06 F150 w/3-vlave 5.4L V8. When he bought it 3-1/2rs ago, the dipstick was "stuck" in the tube. We managed to get it out breaking the dipstick and replaced it with a new one. He runs around 6000-8000 miles per oil change, puts seven quarts in, drains seven quarts out, NEVER checks the oil. Now we know why the dipstck was stuck!
Think I mentioned in a post here 2-3 weeks ago that CUMMINS recommends oil change intervals by the amount of oil an engine burns over so many miles. In an engine that has over $100 worth of filters plus eight to ten gallons of oil, an
oil change costs BIG bucks! But according to the engine manual for the VT-903 in my old White RoadBoss II, with only a quart of oil needed per 1000 miles, 10,000 mile service intervals were recommended. I did between 2500 and 3000 miles per week and added one, maybe two quarts per week. The co. would service my truck every six months if I bitched long enough. I really didn't care if they changed the oil & filters, but wanted them to grease the steering gear & frt axle so it steered easier! When I'd back it out of the shop, it was like the truck had power steering!
And yes, the old K-series singles use 1-1/2 quarts of oil, the Onan in the 982 uses 1-3/4 quarts but has a filter. The K-series get changed every 30 hours, the Onan every 50. Better to change the oil sooner than later.
