Originally posted by CharLac I remember my Mom talking about crossing over the Rockies with her family way back when and mentioning how her Dad would have to back up some of the steeper grades. I guess the cars back then did not have a deep sump in the oil pan so the engine would starve for oil going forward up the hill. In reverse the oil would collect at the front of the engine and allow the oil pump to do it's thing.
When I was a teenager I used to work for the local city bus transit. They mostly used GM city buses, but also had the occasional Mitsubishi city bus (with their honking big diesel V8's that sounded marvelous), a few Can Car buses (think they were made in Thunder Bay) and a few older...even some late '40's electric trolley buses. Geez...I've really drifted here.
Anyways, back to the original point. Oil lights coming on in some vehicles that had shallow oil sumps. One of the jobs I had at Transit was checking buses...in regards to # of passengers both sitting and standing, time checks at certain bus stop points, bus number, run number, etc. Mostly I sat in a specialized trailer, but on occasion I rode on the bus and usually at the front of the seating area, with my check list.
Most of the roads here, are flat. But on this route, there was a rural road the bus would go down that had a significant and long incline. Three quarters of the way up, the buses red oil light would come on in the dash and a minor gong-like sound, would sound. I was startled the first time this happened and asked the driver why that sound and re light activated. He said, because of the incline, the engine oil would floe back in the sump...and not have a deep enough oil supply for the oil pump to suck up. As soon as we levelled out, the red light would go out and the gong would stop.
Now that doesn't sound quite right. But then the bus company back then, even with ur fierce winters, would not use anti freeze in the cooling systems of the buses, as their theory was the buses were always in a heated garage and when they were out on their routes, they never shut off. So as long as that continuted, the company could save on not using antifreeze in the hundreds of buses they had.
Made me think as the routes were invariably on flat, level roads, maybe they could keep the engine oil levels at a minimum. As far as I knew there was only was significant grade. If you minimize the oil level by a quart or so...over hundreds of bus engines...that could be a significant savings due to economy of scale. But I'm just guessing about the oil. I could be wrong. This was the 17 year old mind of mine speculatin'.