Ampol shareholders are in for a windfall after the company said it would use higher than expected proceeds from a property sale to buy $300 million in shares.

The fuel supplier on Monday said it collected $635 million from the sale of a 49 per cent interest in its property trust to Charter Hall and GIC consortium, announced in August.

The company had expected to collect $612 million but the costs of the sale turned out cheaper than expected.

This saving, along with improved trading conditions, lead management to offer shareholders the chance to take part in the buy-back.

The off-market buy-back will begin on December 7 and be completed in the first quarter of its 2021 financial year.

Shares rose to their strongest level since March, and were higher by 4.47 per cent to $29.70 at 1409 AEDT.