Here is a quick blurb on the B234 engine…
en.wikipedia.org/wiki/Volvo_Redblock_Engine#16_Valve_Variants
…including removal of the balance belt.
Engine oil capacity is 8.1 US pints including the oil in the (small) oil filter.
Add 0.7 quart for turbo versions.
From 1989 to 1992 the B234F was found in the 700 and 900 models.
A detailed how-to on engine maintenance is found here…
www.volvoclub.org.uk/faq/B234Ftimingbelts.htm
Information on the PCV system is found here…
www.volvoclub.org.uk/faq/EngineSealsBeltsVent.html
…keeping in mind that EU smog differs some from USA. Share the VIN for your Volvo so we can confirm the model version which will lead to the correct PCV info.
The engine will operate on low octane fuel but not at maximum efficiency as the ECU/sensors inhibit optimum performance. The engine thrives on high octane gas and this is where maximum mpg may be obtained. Measuring mpg is a bit tricky especially if one employs the "last fill-up" method. Given the car's frontal configuration and sedan aerodynamics mpg at the higher speeds may vary greatly from tank to tank. On my '86 245 B230F the mpg improved measurably once I resolved the sticky caliper issue. The lubricant type in the transmission and diff may influence mpg especially in cold weather during short trips.
"…what the car is worth?"
$65 salvage, $850 auction, $1,100 to $1,500 blue book, $5,000 Volvo Lover and $50,000 in mint condition after 2089.
George Dill