From the outside of the front row, Orudzhev grabbed the lead from slow-starting polesitter Aurelien Panis away from the line.
But running a low-downforce set-up, in contrast to the chasing Dillmann on medium-downforce, Orudzhev was frequently under pressure in Spa's second sector. A severely flat-spotted tyre added to the difficulty of Orudzhev's task.
"That was quite long," said a deadpan Orudzhev. "I didn't know what lap it was during the race, and only found out halfway through the last lap that it was nearly over.
"I just knew if I didn't make any more lock-ups, I should be able to make it."
Dillmann briefly took the lead on lap 15 of 21 when Orudzhev locked-up his front-right wheel and ran wide at La Source. The pair ran Michelin-to-Michelin into Eau Rouge, where Orudzhev lifted, only for the SMP-backed driver to slipstream back into the lead at Les Combes.
An earlier, spectacular, lock-up by Orudzhev into the Bus Stop chicane had left a visible flat-spot on his front right tyre.
"In that one massive moment, I thought it would kill my race," continued Orudzhev.
"Normally you can't survive with a flat spot that size for more than a lap."
AVF racer Dillmann would finish second by 0.229s, having gone side-by-side with Orudzhev into Blanchimont on the last lap, but the Frenchman was satisfied with his fifth consecutive podium.
"I didn't know which level of downforce to use, so in the end I asked my engineer to decide," said Dillmann.
"I think he made the right choice. My problem during the race was I had Louis [Deletraz] right behind, so I needed to compromise some of the time in order not to lose a position to him. But I am happy with the result, and I think we put on a great show."
Fortec driver Deletraz also used the low-downforce set-up to claim third, and had several passing attempts on Dillmann at Les Combes.
"Tom needed to create a space during the second sector so he could get a run on Egor and avoid coming under attack, so sometimes he was braking in some unusual place, but I am really happy with the podium," said Deletraz.
Teo Martin Motorsport runner Yu Kanamaru was part of a train of cars behind Deletraz in the closing laps, and would take fourth, 0.6s ahead of Lotus racer Rene Binder.
Pietro Fittipaldi was knocked off into the gravel at the Pif-Paf on the final tour by Hungaroring winner Johnny Cecotto Jr, promoting RP Motorsport's Vitor Baptista to sixth.
A move into the GB3 Championship for 2022 put all eyes on 2020 British F4 champion Luke Browning. On his return to competition in the UK, following a season in German F4, the Hitech GP driver lived up to expectations to see off the challenge of rising Swedish star Joel Granfors
Cadillac driver Sebastien Bourdais feels LMDh manufacturers are playing a “cat and mouse game” in testing for the 2023 IMSA SportsCar Championship as they attempt to understand their respective strengths.
The 2015 Formula Renault 3.5 season will be notable for being the last with the French company's backing but also produced a worthy champion in Oliver Rowland. PETER MILLS evaluates this year's crop of drivers
Last year's field was extraordinary and hard to match, but the Formula Renault 3.5 grid will still have plenty of talent this season. Glenn Freeman runs through the field ahead of this weekend's season opener
Landing the Fortec seat that took rising star Robin Frijns to the 2012 FR3.5 title was already a good sign for Stoffel Vandoorne. Then McLaren took him under its wing. Peter Mills tells Vandoorne's story so far