* Writes down 85 million euros on Avis Europe stake
* No change to 2008 guidance, due Friday
* Shares gain 6 percent at 1027 GMT (Adds details, analyst comment, shares, author byline)
BRUSSELS, March 4 (Reuters) - Belgium's largest car distributor D'Ieteren has taken an 85 million euro ($107.5 million) post-tax writedown on the value of its stake in Avis Europe in its group accounts.
"In light of the deterioration of the economy, the board of D'Ieteren has reviewed the carrying value of the company's investment in Avis Europe," said D'Ieteren, which owns 59.6 percent of Avis Europe, the continent's biggest car rental company.
It added that the writedown did not affect D'Ieteren's loan arrangements or compliance with debt covenants.
There was no change to its previous guidance for its 2008 results, which will be released on Friday, D'Ieteren said.
In November, the group said it expected 2008 pretax profit to be slightly lower year-on-year due to the economic climate. In 2007, D'Ieteren reported pretax profit of 194.3 million euros.
Also in November, the group said D'Ieteren Auto was expecting a market share slightly below 20 percent in 2008.
Excluding minorities, D'Ieteren's shareholding equity should come to 1.02 billion euros at the end of 2008, KBC Securities analyst Pascale Weber wrote in a note.
According to the Belgian Federation of Car Industries, brands distributed by D'Ieteren had a market share of 19.19 percent in February.
D'Ieteren distributes the Volkswagen, Seat, Audi, Skoda, Bentley, Porsche and Lamborghini brands.
Avis said on Wednesday that underlying profit before tax on continuing operations for 2008 came in flat compared with 2007.
Shares in D'Ieteren were up 5.9 percent at 1030 at 98.5 euros. (Reporting by Anne Jolis; Editing by Will Waterman and Rupert Winchester) ($1=.7906 Euro)