Bamaro, i've always taken a half litre (nearly an eigth of a US gallon, I suppose your quarts are different to an Imperial quart too)per 1000 km (600 miles) as an acceptable oil consumption in a new car. That would be a little under a quart per 1000 miles.
But what sort of driving had you been doing prior to this trip? Because if you'd been driving around town, short trips, then what you might've seen is fuel dilution.
I used to have people questioning me all the time about sudden oil consumption increases. They'd drive their car to and from work, or around the town to the supermarket and to pick up the kids from school, then take the car away on a long freeway trip. They'd be amased to find when they checked their oil that they had used a litre or more oil on the trip.
Well, they hadn't used the oil on the trip, they'd used it running around town but the engine had 'topped up' the oil level with fuel dilution from cold running - the fuel in the crankcase had never been evaporated because the engine hadn't reached a high enough temperature. Then when they head out onto the freeway, the engine temperature climbs and stays high and the fuel dilution evaporates, and the oil level goes down.
Fuel dilution happens in all engines, but usually in a petrol (gasoline) engine it is burnt off.
I remember once when doing a trial of a generation 5 railway locomotive HDEO in a group of GE locos that the viscosity of our oil was dropping and causing the oil to be condemned at about 90 days - this oil eventually lasted over 300 days in service once the problem was solved.
There was fuel dilution happening, by the time 90 days were up there was nearly 10% of fuel in the crankcase. The operator was concerned that this generation 5 oil was suffering viscosity drop when a competitors generation 4 oil wasn't.
It took a lot of used oil analysis - including gas chromatography because the fuel was being 'topped' (that is the lighter components were boiling off) to discover that there was just as much fuel dilution in the competitive generation 4 oil as in our generation 5 oil.
But the generation 4 oil was oxidising and thickening and the fuel dilution was thinning it and that balanced things out so the oil/fuel mix remained at approximately the same viscosity as the new generation 4 oil.
Once the fuel dilution problem was solved, they installed low sac injectors, the viscosity drop disappeared and the generation 5 oil lasted more than twice as long in service as the generation 4 oil.
